If he wants to stay, he will stay long enough to burn the security deposit if he decides not to pay. 

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

Can I ask a regular institution to provide this kind of loan?

Regular ADU permits would not work as the setbacks would make the rest of the lot unusable.  

Or is the procedure identical to setting up a regular series LLC, except that the 401k trust will be the sole member, instead of an individual person?  

For example, you might be able to pay higher loan origination fees in order to secure a lower long term rate.

Debt is from a mortgage on our primary residence and student loans.I'm now in a situation to either reduce debt or increase my regular income (via paying cash for rentals/purchasing notes/something like that) to a point where my dti would be more attractive to lenders.

If you do not have $50,000 liquid cash to invest, we do have ways to secure start up funding that can be discussed at a later time.You will first start by purchasing your first turn-key rental property from us for $50,000 cash.

Additionally the root systems of these large trees can damage the main water lines to the street, pop up sidewalks near the building, and crack the foundation of the building itself.A regular inspector is not going to do the plumbing.

High turnover; late payments; dodgy complaints; regular tenant-induced damage, and so on...