Having a vouch from a scammer won't really help your business. Also, even though you are saying they are "privately" cracked, the original owner still has access and can recover the accounts at any time, seeing as this is illegal. Caveat emptor - buyer should know that these accounts are sold as-is, subject to any and all defects. There is no telling when these accounts will die, but it is very unlikely that it will be for long.