They are two separate sales agreements. 

So when we did not receive any response to our emails for several days, this naturally triggers concerns and emotions.

The risk of "piercing the veil" applies more to LLCs when personal and business finances are not properly separated, not necessarily to individual landlords renting a portion of their home.A more practical approach is ensuring you have a solid lease agreement, sufficient liability insurance (including an umbrella policy), and properly reporting rental income and deductions on your tax return (Schedule E).

I see two separate issues.1.

Separately, the benefits and disadvantages of renting to Section 8 is a topic of extended debate on this forum.

They are all on separate parcels, paid off and occupied by long term tenants.

this is the distinct different between being an actual lender like a bank .. and an investor in a fund.. two very separate transactions.. when you lend and receive collateral on the asset you get paid when it pays off or the borrower refinances etc. 

Another idea could be to see if the HVAC system can be adjusted or modified to better separate the airflow between the units.

This is a unique home and it actually has a full kitchen, 2 bed and 1 bath downstairs and I think it might be well suited as a very large vacation rental(entire home) or both floors being rented separately at some point in time.  

Property managers cannot touch your money, It has to go into a separate account managed by the broker.