Will need to know a lot more to evaluate his situation.

@Devin Scott have your friend call a mortgage broker and explain his living situation.

Yes, exactly, you want to speak with a few brokerages- and let them know your current situation and find what works for you! 

So that question doesn't apply to this situation. 

@Jay Hinrichs   You may be right, the deals I make thought wholesaling, if I am dealing with an agent, he/she get the full comision, and they normally love me after closing, if I am dealing with the seller directly, I feel I am helping them, I try to do a win-win deal, I have close some deals with zero profit but in those cases I was happy because the seller was happily resolving their situation, right now I am more focus on building my portfolio with friends rather than make more quick bucks

Just make any tenants that come look aware of the situation, so they aren't surprised by it on the day they move in. 

It could already be  legal 3 flat but if you need to request a zoning change its not just sending in a letter.PM me some specific details and I can help you figure out your situation.

It's a hard situation since my son is being an as#hole about it. 

Does anyone on this thread have any advice on such a situation?

I will now look at these situations as positive because it is bringing opportunity.