I know it's not illegal or prohibited on the forum to buy accounts or offer to buy them, but since they used a terrible technique to try to convince me to sell my account, I suspect nothing good or honest could come from there. I could be wrong, but just in case, I'm leaving this here so you're all on alert!
Lol, I am not sure why he sent you a PM when there are a lot of highly reputed accounts. I don't think they have any legal service to promote here. If there is, then they shouldn't be looking to purchase a forum account. Legal services are always welcome here, either promoted by newbies or high-ranking accounts. They could make announcements themselves and advertise in various ways.
Otherwise, I noticed you have a loan history. They want to purchase your account, create some more loan history and then finally exit scamming. At least they aren't asking to purchase your account with a good intention. However, since PM isn't verifiable by me, I am not tagging based on this thread right now. Rather, you may report to the moderator for unsolicited PMs, and admins would take action for that, although account selling isn't prohibited here.