I can however say that the scenario you outline is not a wholesome one - agreeing to one rate and then paying some kind of supplement on the side.

It includes but is not limited to monies derived from Social Security benefits, supplemental security income, unemployment benefits, other retirement programs, child support, the Aged, Blind or Disabled Cash Assistance Program, Refugee Cash Assistance, and any federal, state, local government, private, or nonprofit-administered benefit program."

Those are the owners that professional landlords prefer to take advantage of purchasing at a low number, value of income property being determined by NOI, and then bringing the rent to market rate.If you are a hobby landlord, which it sounds like you are,  then supplement their rent at whatever level you feel comfortable with.

Scary.I am surprised that I didn't see anybody suggest that the tenant just go get themselves a window unit to supplement the central A/C.  

Will he have something to supplement their income until he goes back to work?

By the time you get there, you'll know more.And I actually made good supplemental income in college from sitting at poker tables, but that is a whole other story.

Illogical, irrational and not based on any known facts to support the theory that supplementing tenants rents retains them longer.

I'd also have her adult son do the same, but I would be more looking for history on his part and making sure he is a good tenant when he is staying with her and not be as concerned about the financial obligations on his end (unless it is needed to supplement the mother's).  

My plumber I use only charges $25 to set toilets but he is underpriced so I get a sweetheart deal - he has a good day job and this side money is to supplement his retirement   - I'll have to find a new one when he's ready to hang it up.  

Smartmove is the supplement after they pass your basic criteria.