They’re questions of supplemental income and do not go against fair housing laws.

The impetus for REI is to supplement retirement income.What's the universe of personal risk in a default / foreclosure situation?  

I still have to supplement with electric and propane heat in the winter but they look better than window units from the outside.  

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.

I haven't taken it off of Airbnb yet and don't have plans to but I do plan to speak with a lawyer and draw up a separate supplemental contract as my Airbnb is growing rapidly and I feel like the extra level of protection couldn't hurt. 

Many companies require you to use their application forms (on-line or faxed/e-mailed), which we do and add our own supplemental pages for info they don't request but we want.Think about the qualities of a good tenant, what your criteria is, and design a process to weed out undesirables and look at credit, criminal landlord history.  

You could just be generic."

Legal zoom is a generic boiler plate blanket set up and usually just good enough to make you feel protected with many loop holes.

The knowledgeable investors I know have their attorney draft one and don't use a generic one-size-fits-all

You don't need to know their names or anything else, but you have to give everyone notice - even if only in a generic fashion.