I don't know about you, but I have no idea how much my stuff is worth. I'm talking about the little things. The t-shirts I don't wear anymore, the old cell phone, the books I don't want to read again. All the things that are no longer valuable to me but may be to someone else. Mercari solves that problem. 

The seller experience on Mercari is designed to help users earn as much money as possible. While it's easy to list whatever items you want to sell, you can also opt to go through a set of questions asking if you have popular items. These include high-value items like phones and sneakers and cheaper items like t-shirts. If you have an item, tap yes, and the app adds up the average that your items sell for to give you a sense of how much you can earn. This process gives you a good sense of what sells best on Mercari and may give you some new ideas of what to sell.

The listing process is quick and easy. You post up to 12 pictures of your item, describe it in your own words and select options for category, brand, condition, and more, then set your price and shipping preference. Based on your price, the app will calculate your selling and processing fee right there and let you know how much you’ll earn. That means no surprises at payout time.

For sellers who want to earn more and enjoy goal-setting, Mercari offers a helpful tool. Just set your earnings goal, and Mercari will help you track your progress, providing selling tips along the way. This is a great motivational tool to help keep you on track, whether your goal is earning more or decluttering. Of course, the selling experience is only half of the equation. If the marketplace for shoppers isn't good, it will be harder to sell your items. Fortunately, the shopping experience on Mercari is excellent for both searchers and browsers. Popular categories are clearly displayed, and you can search for specific products easily. There are deals to be found, but the prices aren’t necessarily bargain basement. And that means that sellers can make good money here.

Mercari is great for selling items that fall outside of major categories. But if you want to sell something from a major niche, you may want to check out an app specializing in that area. For instance, apps that are focused on fashion may showcase your clothes and accessories better and attract shoppers prepared to pay more.

Mercari's prepaid shipping label only covers items under 150 lbs. While you can choose to ship on your own, it might be more cost-efficient to sell larger items on a local marketplace app, so you can arrange pickup with someone in your area and not worry about shipping.

That said, Mercari offers an exceptional experience for sellers and buyers, and if you're looking for a one-stop marketplace app, this is the one I recommend.

Gather round my fellow lazy and busy people, and let me tell you about ThredUP. If your closet is overflowing, but you don't have the time, energy, or desire to spend a lot of time pricing, listing, and shipping each item, get thee to your device's app store and download ThredUP. With the tap of a button, you can order a free "clean out kit" and take care of your closet in a single afternoon. 

While on other sites, you handle listing, communication, and shipping for each item, (as well as figuring out what to do with unsellable items); with ThredUP, you just fill a bag and send it in. ThredUP's clean-out kit is basically just a large plastic bag. You fill it with clothes, accessories, and shoes that meet their criteria. Ship it back, and they list and sell what they can.

While ThredUP won’t work as a side hustle, it's a perfect solution for a one-stop shop for closet cleanout. Consider the money earned a little reward for decluttering. 

The main selling point for Facebook Marketplace is that it is Facebook’s Marketplace. Built directly into the Facebook app, if you have a Facebook account, you won’t have to sign up for a new service, make a profile, or any of the other setup things that other apps require. Communication with potential buyers takes place in Facebook messenger. The ability to use the tools you are already using is incredibly convenient and a good argument for choosing Facebook Marketplace.

But the best feature of Facebook Marketplace is not that you already use it, it’s that everyone else does too. Particularly for selling things locally, where you have a smaller pool of potential buyers, it helps to be on the app where all the people are.

OfferUp is a wide-ranging marketplace for local and shipped items. And I'm not joking about wide-ranging: the listings for my area included cars, a toilet, tchotchkes, and crafting materials just on the opening screen. 

It’s easy to post items to sell, and you can choose between shipping and meeting up with local buyers. This is a good choice for selling locally but doesn’t have as large a user base as Facebook Marketplace, our pick for local selling. It might be worthwhile to list your items on both apps, however.

The original online marketplace, eBay continues to be a great place to sell almost anything. You can choose between auctioning items and setting a price. With a large customer base, you can definitely make some extra cash on the app, but some newer app options are more user-friendly.

That said, eBay is massive and has a proven track record of providing users with a side hustle, so it's worth checking out.

With an interface that resembles Instagram, the ability to connect with friends on the app and share posts on your social media accounts, Poshmark seems to be making a bid to be the social media app of secondhand fashion. While I question whether that’s something we needed, the app does have a large user base and is easy to browse. The app feels more oriented towards buyers than sellers, but since you want potential buyers to enjoy using the app, this may be a benefit.

On Depop, users create shops to sell clothes and accessories. Definitely, the most youth-oriented app we tested, the app would be best for people with a lot of trendy items to sell. You have to make a store to sell things (you can’t list individual items), so the app is a bigger commitment than many of the others.

But if you are looking to build a side hustle, Depop lets you brand yourself more effectively than other apps. Having a store makes it easier to attract repeat buyers. 

Decluttr offers a simple process for selling CDs, DVDs, games, and tech. If you have lots of these items, it might be worth checking out. You scan in the barcodes of DVD's etc. or select the model of tech device to get your payout information instantly. Then you just send in your stuff. 

However, the app is clunky and difficult to use. You can’t shop on the app, but they do pay outright for items when you send them in, so checking out the marketplace for buyers isn’t important with this one.