Renting to Illegal immigrants

[Christian Beyer]

I'm not sure if this has been touched on previously but it recently became an issue that I never planned on dealing with.

My business purchased a duplex back in November, and one of the tenants picked up and moved out with no notice about a month ago. Since then, we found another duplex and managed to get it under contract on a short sale. The current landlord gave the tenants 2 weeks notice to clear out, and when we were touring through it one man asked if we had another unit we could rent to them. We did so I offered them our newly vacant unit across town. When I went to get background checks he mentioned that he and his wife and their daughter did not have social security numbers and were living in the US illegally. 

I called the references he provided for his employer and previous landlord and it all checked out. So far so good, but it has only been one month. Does anyone know the legality of renting to illegal immigrants? I would also like to hear some best practices for dealing with this if anyone has stories to share.