There are lots of places to sell your stuff when you’re ready. The kids today (yes, I just said that) use an app called Depop, so I would start there first. You can also try Poshmark, LetGo and other resale sites that attract slightly older audiences. Write a catchy ad, be as descriptive and honest as possible, and take excellent photos. You can search those apps and ebay to get an idea of how much your stuff is selling for.
If you have something you think might be worth a few bucks more, take it to ebay, where you will probably find more serious buyers who are willing to pay more.
If you find you’ve got a gift for reselling pleather tube tops, you might even want to start buying and reselling vintage clothes. It’s a $28 billion market, according to estimates from analyst firm GlobalData. While I wouldn’t recommend selling on Facebook Marketplace (it draws a very general audience), the site is a great place to watch for free or low-priced vintage clothes and to make “in search of” posts. People might even sell you entire boxes (so-called “lots”) full of clothing for a very fair price just to have it out of their house.
You might even offer to sell other people’s stuff for them. Say your cousin has lots of clothes and you have lots of time. You might work out a deal where you list their stuff and take a cut of whatever gets sold.