My unit count is much less but the duration is around 50 years (combined my mom’s rentals and my rentals) without paying a tenant to leave or having to do an eviction.  

I know legal ownership and beneficiaries can increase that coverage in a number of different combinations, but are there ways you can think of to expand coverage specifically with the solo 401k's?

Have you considered combining "glamping" with cabin rentals for short-term rentals?

Lesson learned that location is always no.1 factor and quality of renovation is the momentum of it and those two the most profitable combination.

Combine these 2 and brown field is likely to set itself apart from the other local secondary airports. 

It was logical to combine this.

Actually, the combination of all that you mentioned contributes to it. 

We did get negotiate money from them to help with roof repair, but now know they were not honest on their disclosure.Our inspector missed code violations, HVAC issues, pipes that had been worked on and issues hidden that had occurred while sellers lived in the house, signs of drainage and water damage inside the house that had been painted over, completely blocked dryer vent...and we are finding more daily.We have had the house looked at by a structural engineer and HVAC techs that has told us we need thousands (likely tens of thousands) of dollars worth of repairs to make this property able to rent and come up to code for rental. 

Everyone has a unique combination of skills and circumstances. 

Yes you can buy 2 properties as long as the combined price is the same as the net sale price of the one sold @Dave Foster is the expert and I use him for all my 1031 transaction.