There is much games were you can sell your account. Mostly they are massive multiplayer online ones. There is many sites that offer to sell your account for $$$, but it price is usually very different for games. Like in WOW you can get from 100-2000$ depending what your character ingame have, legendaries is increasing much value, but with time prices drop cuz ppl get more same items and its not so rare anymore. Usually is used bots to lvl up, cuz its require usually around some weeks to max ot level.
Best to try is to get in some game beta-testing phaese for free and sell it from 10$ - ...$ depending on demand. You can try with skins/items, but you need usually much time/investment to get it if you ever get, it randomness
But yeah there is many scammers, cuz of way earning easy money, by stoling accounts or getting betakeys