Jack and John make good points. But you know me. I going to suggest something else. If he can get you records that meet your standard for preparing a timely filed return, and you can get paid to do the returns, I say go for it. I would not worry about how to help him avoid his debt. Or if you feel like helping him out of the crack he got his own tail into, help him do that later. After all, HE'S late at everything, right? I know that's not very sophisticated advice, but I have never understood why we treat a late return differently than any other. I would avoid a lot of hand holding, unless you normally do that for everybody. If he owes $170,000 in taxes, he made a lot more money than I do, and while I was making estimated tax payments, well, you know...
And, the part about a family member getting a letter? You might check on the existence of a spouse, cause that's all I can come up with on that one.