Honestly. I would suggest buying from a website like accountwarehouse, or any other reputable account selling website. Although the accounts they buy can always be recovered, almost all of them offer some type of coverage in case that happens so you don't end up losing your money. Not only that, many times the process of selling accounts to them is somewhat rigorous (picture of id, phone number, address, recovery test, etc) so many scammers stay away.
If you still insist in buying from a user, I suggest you look for someone with very good rep (preferably a mm, staff member, etc) and make sure to read the stickies in the account selling sections which offer some advice and some harsh realities that you might not want to hear (like the fact that ALL accounts are recoverable by original owner, no matter what)
Good luck