There's a plethora of available opportunities and places to source things to resell online. But the best place to start, if you're just in the beginning phase, is with your own closet/house.
Start by going through your clothes and pulling out everything you no longer wear, no longer like, or that doesn't fit. Same with stuff around your house - collectibles, valuables, electronics, small appliances, art, video games, board games, toys, comic books, etc. A lot of seasoned sellers will give this advice out to newbies and suggest that they take any profit from sales from your personal items and reinvest that into buying inventory. Personally, I did a combo - I collected comic books for years with the sole purpose of reselling them eventually. At the same, I decided to start selling a bunch of toys & collectibles that I no longer put out on display. They'd been sitting in storage bins for almost a year, so it was time to let them go. I also raided my closets and sold some of my clothes I was no longer interested in or that fit me. This way, technically, I'd be in the black instead and able to take a couple bucks to the thrift store and not have it come directly out of my pocket.
The biggest and most recognizable thrift store across the country, Goodwill. It definitely has it's pluses and minuses and still remains a solid go-to for many thrifters & resellers.
The biggest con to shopping at Goodwill is the rising prices. Spend any time in Facebook groups or Reddit and you'll read endless posts & threads about how GW is raising their prices for items of little to no value. I found a thread on Reddit that was interesting and can shed some light to a few reasons why the prices have increased:
It seems like the biggest culprit to the higher prices is that GW now has Goodwill Auctions. In the above Reddit thread, the OP (original poster, the person who started the thread) states that they are instructed by corporate to send certain donated goods to shopgoodwill online. They receive a list (BOLO = Be On the Look Out) of brands or goods that online wants for their auctions. Then the physical store staff is instructed to raise their prices of the remaining items to make up for what was sent out. Now less people are coming in to shop because either the prices are too high or there is not enough things of value to buy - or a combination of the two.
Having said all that, there are still gems to be found at Goodwill - and for the clothes resellers, lots of what are "bread and butter" brands. I still pop into Goodwill from time to time because I can still find things to resell, especially vintage clothes due to where I live (lots of retirees). Plus, the Goodwills in my area offer 50% off a different color tag each week. In some areas, though, there are no discount days or weeks, but in others some will have $1 Dollar Days or 50% off days. I'd definitely check out your local Goodwill and talk to an employee about any special store-wide discounts, veterans/military discounts, or senior discounts.
Goodwill auctions can certainly be a good resource. It's been a few years since I've tried my luck and the feedback I'm seeing online is the same that I remember. You may score a good deal on a valuable item, but the shipping costs are SUPER high. This is definitely a turn off for most online buyers in general, so no surprise that resellers & flippers are not using GW's online auctions as a resource.
Resellers and flippers swear by Goodwill Outlets aka "The Bins". You are able to buy a lot of stuff for very cheap because they charge by the pound - no matter what you are buying. High end, low end, bread and butter, jeans, jackets, boots, tank tops - it all goes in a pile that is weighed and you pay per pound.
If you join FB groups and/or Reddit, you'll see the "bins" get mentioned all the time and lots of people asking what they're like and for tips & tricks. The majority of the suggestions are a combination of the following:
Unfortunately, these reseller havens are not available in every state, nor are they always in convenient locations. For instance, I have to drive an hour and a half to get to the bins in my state AND the price per pound is higher here.
"Savers, Inc. headquartered in Bellevue, Washington, US, is a privately held for-profit thrift store chain offering second hand shopping. ... Savers is known as Value Village in the Pacific Northwest of the US and most of Canada, and Village des Valeurs in Quebec." - Wikipedia
I wish there were Savers in my area! I moved to a different part of my state a year ago, and where I moved from there were a handful of Savers. I used to use them as a resource when I was doing upcyling and trying my hand at flipping online. I found their prices to be fairly reasonable, but at that time I wasn't looking at clothing so I have no personal experience with that. I was there looking at hard goods. Based on what I see in the groups & forums, there are still deals to be had at Savers - and to my knowledge, they have no online selling going on, so you might experience a lack of inventory because of the employees, someone got a good item before you, or just simply no one donated anything good.
Another staple of well-known, national thrift stores. No additional online sales or auctions, so if you're into this one, check your stores often and try to go to ones that are near wealthier areas.
Local thrift stores that aren't national chains
Now here's where some real steals and deals can be found. There's so many different little thrift shops that aren't big well-known chains, so you will probably have some decent "luck" finding really good stuff to flip. There's one small local chain of thrift stores in my area that have 50% off sales of their entire store once a month, and 50% off men's clothes 1x month, 50% off women's clothes 1x month. And I found this sale day by just happening to walk in that day. Talked to the cashier as he was checking me out and suggested I sign up for their newsletter. Now I won't miss any sale days! The drawback with this little local chain is that they separate out what they think is high end or valuable clothing and call it their "boutique" section. So 50% off days make the price tags on those items easier to justify the spend. Luckily, though, they miss a good number of high end brands and they're mixed in with the regular clothes. Also fortunately, they have a flat pricing structure like $3.00 for short sleeved shirts, $4.00 for skirts, $9.00 for jeans - but at 50% off these are decent deals, especially when I can find those hidden gems.
Goodwill definitely misses things all the time, as well, so when you're out sourcing and have the time to really go through everything, I think it's definitely worth the effort.
Plato's Closet, Clothes Mentor, Buffalo Exchange
These "thrift" stores are much more demographically focused and tend to regularly price things similar to prices on Ebay & Poshmark. However, you can sell clothes to them for cash (or store credit) and they have sales all the time. The BEST time to shop at these places are when they have 70, 80, and 90% off sales. On 90% days, you'll be able to scoop really good stuff for $.60 - $2.00! Follow them on Instagram for all their updates!
So this is basically a built in weekly resource for everyone! I haven't done the garage sale thing in a long time, but there is definitely good stuff out there to get your hands on - especially when it's towards the end of the day and they just want their stuff gone. Or if you offer to buy all their [specific item] you'll probably get a killer deal, like offering to take all their clothes for one flat price or their records or their comic books. People are holding these sales because they want the stuff gone and 99% of the time, whatever doesn't sell is going to get donated anyway. Lots and lots of flippers and resellers hit garage sales regularly to get their inventory - you'd be surprised at just how many people don't want to go through the hassle of listing anything online and will totally sell you something for a super low price that you can turn around and make a tidy profit on!
The best place to find out where and when garage sales are happening are by checking on craigslist. Easy peasy and free!
"An Estate Sale, also called a Tag Sale in some parts of the country, is a way of liquidating the belongings of a family or estate. ... Items are marked with a selling price, and if you want an item you usually pick it up and carry it with you until you are ready to check out." - Wikipedia
Estate sales are where you will probably find seasoned resellers, hardcore thrifters, and full time sellers. I have only wandered into estate sales when they just happened to be going on in my neighborhood and I was out on a walk.
To be successful at picking at an estate sale, it seems like being one of the first in the door or arriving at the tail end are the 2 best tricks to getting the good stuff or the good deals. The prices might be higher, though, so be forewarned. But as you get better at selecting high ticket, high value items, you might be willing to pay up for what you find.
Facebook Marketplace, LetGo, OfferUp
Some people have mentioned being able to find good deals for cheap by using these apps & resources. I think if you're curious and have a few minutes, take a look. Usually you'll have to drive to get the things you want, but I think there are some sellers willing to ship. Some sellers on these apps kind of use them as an online garage sale, so again, they just want the stuff gone from their house.
There's a whole FREE STUFF section - you never know what you'll come across and certainly anything you can get for free and make a profit on is 100% profit. Also, people on CL will use it as a sort of virtual garage sale, so again, there might bargains if you're willing to take the time to look.
Church Rummage Sales
These are apparently a goldmine for resellers - especially clothes. Fill a bag specials and low prices make these sales something to seek out.
Clearance sales at big box stores and department stores
This is sometimes called retail arbitrage. "Retail arbitrage refers to the act of buying products in your local retail stores and then selling those same products through online marketplaces for a profit. The most reliable source of products is generally the clearance racks of stores like Walmart, Home Depot, and Target." - Onlinesellingexperiment .com
There are definitely good deals to be had here especially when the discounts dip down passed 70% off. A lot of Amazon / FBA Amazon flippers and resellers do this in crazy high amounts. Just like all these resources, it might take time and patience to sell, but once the sale happens, the profit margin is pretty good.
There are definitely some flippers & resellers that use dollar stores for retail arbitrage as some of these types of stores sell name brand stuff. Again, it'll take time and patience to turn the item into a sale, but at a $1 apiece, the profit margin will be good.
Family & Friends
Good old family and friends. Everyone has clothes and stuff laying around that they don't want or use anymore. Why not ask if they would be willing to give them to you to sell? Some family members might want to be supportive and give you great stuff and let you keep all the profit. This could get dicey with friends if they expect a kickback, but if you agree on a percentage split up front, there should be no problems.
At first glance, this may seem gross and unacceptable to some and honestly, it doesn't strike my fancy, but people do this. There are youtube videos showing people finding dumpsters that are open or unlocked behind big box & department stores and going through what they toss out. These items would be free, so profits from sales are 100%, not bad for a bit of time digging through some garbage, right?
I have not been to any of these stores or warehouses in person, nor have I ordered anything online, but again, a quick google or youtube search will probably answer any and all questions about this as an inventory source. A quick google search found these 3 online sites which might worth looking into depending on your level of reselling and how much money you're willing to put up.
It seems like the resellers are about 50/50 on whether or not these are good investments. The prices can be low, especially on Poshmark, but are generally $25-50 on average. Goodwill has their "Blue Boxes" and ThredUp calls them "Rescue Boxes". Poshmark will either go with mystery box or reseller box.
There are tons of youtube videos unboxing their mystery box purchase if that will help give you an idea of what to expect. Again, the feedback is pretty mixed - for every person says their box was great, there's another that will say they got crap and it was dirty. If you're a risk taker and love to live on the edge, why not give it a try? I haven't bought one, but am considering putting a couple up for sale, although mine will be full of toys & collectibles that I don't feel like selling online for a few bucks a pop.
As of this writing, eBay is no longer allowing mystery boxes without the contents being shared, so not very mysterious.
Goodwill Mystery Boxes
Goodwill offers their own version of mystery boxes called Blue Boxes. You are able to select the type of mystery blue box you'd like such as vintage, jewelry, jackets, sports jerseys, etc. They restock their mystery boxes every Friday and range in price from $9.99 to $74.99.
ThredUp Mystery Boxes
Alternatively, ThredUp offers their version of mystery boxes called Rescue Boxes. You are able to select the type of rescue box you'd like such as mixed clothing, denim, shoes, Coach or designer handbags, men's clothing, etc. They range in price from $16.00 to $110.00.
Poshmark Mystery / Reseller Boxes
Search in the search bar for mystery box or not-so-mystery box sellers and don't forget to look at their reviews before buying.