Questions about selling the rights to my books

So i've got several full-ish length novels I've published on kindle years ago that I'm just not up to do marketing/ads with and I'd honestly just like to sell the rights to someone who'd like to buy them. They're about 40k+ words each if it makes any difference.

Not sure if there's a specific site or method i'd go about doing this with since I've never done it before.

I've also got maybe over a dozen flash-eroticas that I've written but since they're more adult-types of content I'm not sure about resale value especially since I don't think you can even run ads on stuff like that.