(for instance a while back there was some concern about people here illegally applying for welfare would get them deported....is it something like that?

Told the undocumented tenants if they complained, he would report them to the authorities and have them deported.  

They simply overstayed their visa or the government decided they should be deported for some reason.Depending on what type of visa someone comes to the US on they will or will not be given a social security number. 

The only difference between resident and citizen is the possiblity of deportation (unlikely except for committing serious crimes) and no voting rights.

Tax the snot out of deporting capital.

With the new changes in immigration policy and less fear of deportation for many, more buyers and renters will feel empowered to speak out against bad lending and land lording. 

Unsubsidized families with very low income, Drug addicts, recovering drug addicts, very young renters, illegal aliens subject to deportation with no notice, etc... (???)

I wouldn't push it.What would happen if this illegal immigrant is swept up and deported for violating immigration law?

He left her so destitute that if she does divorce him and he gets deported, she is responsible for his tax debt so they’re still married.

Since illegals are subject to deportation they may not be as superbly underwritten as suggested.