Ask HN: Dev experience buying an existing website?

Anyone have experience buying an existing site from something like flippa and building it out from the developer side?

I heard most of these are scams, but was wondering if there's good methods for finding a site worth spending dev time.

Mental model (knowing very little) about the process is like house flippers that take existing run-down houses, renovating and re-selling for a markup.

Except I'm fine w/ just building the site for long term.