If this is one of your first rentals I would also suggest you get copies of lease forms from them, they are cheap and have withstood the tests of time.You can't consider their age when renting, that is discrimination.You can't deny them because you don't think their relationship won't last.You can't deny them based on debt to income if you don't have listed rental criteria with specific guidelines of what debt to income ratio you will accept.If there is anything subjective in your rental criteria you are likely setting yourself up for a possible discrimination suit.Renting a property is more of a science than an art, make a listing of rental criteria, if they meet the criteria, rent it to them. 

One person has the voucher with a live-in friend with a job, making more money than an honest family.

Much more of a business than an investment activity.

The 401(k) has higher contribution limits than an IRA, so a self-employed person can add more of their income to the plan on a tax-sheltered basis each year in addition to have investment flexibility as a self-directed plan.  

I don't think it took me much more than an afternoon to finish it. 

Are there any other methods out there that I have not exhausted?

That policy will provide additional coverage (usually sold in increments of $1,000,000) that is triggered if the limits of underlying Personal Auto, Home, and/or Dwelling Fire policy are exhausted. 

I'm really reticent to pick up a property that has more than an incidental 1 bedroom here or there.

Humidity can be caused by humidifiers, not running the exhaust fan when showering or even occupants of the space can create humidity.

I was just informed that the exhaust pipe for the dryer is clogged and the tenant wants me to fix it.