I see this as a professional courtesy and treating others as I would like them to treat me. 

Having lived and worked in markets that don't give the same returns, this area's a treat.

Because if it's just money, and no skills or talents to get the projects done more quickly and cheaply, than I would treat them as a private lender as far as return on their money goes.

Selling a membership interest or partnership interest in an entity would likely not qualify since it is not treated as buying real estate for tax purposes. 

This is a business for you at that point, so you need to treat it as such.

I would call a few termite companies to give estimate to treat.  

Don't rent to couples.Screen your tenants and treat it like a regular rental.

If I sell a rental that I acquired using 100% qualified retirement money from a Solo 401(k) and immediately deposit the proceeds back into the Solo 401(k) would I have to do a 1031 exchange purchase or purchases to avoid capital gains or is this treated differently within a Solo 401(k) retirement fund/plan? 

Your property can be treated as both an investment property and a personal residence.

In this scenario, where I’m going to have to hire a cleaning company and possibly treat the unit for the smell, I feel entitled to the security deposit.