Rental Receipts for Tenants Social Security

[Ryan L.]

First time poster, but I have been following the blog for awhile now. I have my first question that I was unable to figure out myself.  I recently signed new tenants to my 3 bed/2 bath home.  It is a mother and her son with his girlfriend.  The son is a caretaker for his mother (she can not read or write).  The tenants are asking for a rental receipt for his mother for $400 (total rent is $485). I would see no problem to this except for the fact that it will come in one check. He collects the money from his mom in cash (from Social Security I assume) and writes a total check to me for the full amount.  How do I handle the rental paid receipts? I believe he wants 2 separate receipts, $400 for his mom and $485 for him, but as I can't verify the $400 actually came from his mother - is this legal? Thanks in advance for your help!