Buyer beware a lot of people make a living selling and flipping sites that are ahem... not worth the money. In fact expect 99% on some of those sites to be trash and spend a lot of time on DD. There are probably some good ones on there.

I recommend participating in forums and getting to know people that way, then reach out to someone if you’d like to buy their thing. Mostly they’ll say no but you never know your luck.