Most listing agents train their clients to avoid FHA offers because of the extras that come with. 

Ignore the loan when trying to factor in the possible tax implications as paying off a principal balance doesn't do anything tax-wise.

There was a property at the auction that sold at market, however it had a federal tax lien of over 100k attached to it.

If you are setting aside funds for capex, taxes, insurance, or other expenses that don't occur monthly, transfer those funds to Savings each month and hold them there until it's time to spend them.

I have some questions about the material participation rules for the STR tax loophole.

Typically, it just refers to the number of units/leases you have, not the number of tax parcels. 

Another instance of why we avoid HOAs like the plague....

By reaching out to the city beforehand, you can ensure that you are prepared for the renovation process and avoid any potential complications that may arise.

Given that you've owned them for almost 5 years, there is also a good opportunity to do a cash out refinance and obtain tax free money that you can use to expand your portfolio even further. 

I would avoid aggressively pursuing traveling nurses.