We're not going to do any showings (we've put up a lot of pictures so people can see what the room looks like), and we have a comprehensive application form to vet tenants. 

Every single long term rental I have there has been at least 1 lay off in that household.

Since she's a single income household it is getting very hard for her to pay the mortgage.

In your scenario going by number of people may be easier: if you have two renters and yourself living there, 2/3 of household expenses can be deducted from that rental income: 2/3 of utility bills, repairs, etc.I hope this helps!

The affordable units are not subsidized, they are rent restricted, and the max rent you will be able to charge for that unit is based on the following which I pulled directly from a density bonus agreement:The monthly rental rate for each Affordable Unit (which shall include a utility allowance based on the utility allowance schedules published annually by the Housing Authority) shall not exceed 1/12 of thirty percent (30%) of fifty percent (50%) of the Area Median Income, as adjusted for assumed household size and utilities.

I’m curious if there are any recommendations out there for comprehensive books or other sources to educate myself quickly on options, downfalls and benefits of different types of financing etc.Thanks! 

It is one of the most affluent townships in the United States based on average household income.

If I find that I need a more comprehensive solution, I'll look into Buildium.  

I’m seeking advice that can help me form a contract that is in basic comprehensive layman terms.

Sure, go ahead and let 20 people share a bedroom.That all brings us to our local fire codes that in fact limit the number of people per household and/or bedroom, and of course this varies a bit from municipality to municipality.