I’m tempted to do many of the renovations while they’re in the unit, which would help dramatically reduce turnover the next time, but really trying to decide if I should wait 2-3 years or start slowly doing these renovations, since I know they’re needed...eventually.

I have found in business that following the rules just reduces risk.

. ~$200/mo revenue from a power plant on the roof in addition to reduced utility bills will definitely be a selling point for the home, once you've removed the UCC/lien issue of course. 

This will help you filter your results and reduce time wasted looking a properties that don't meet you criteria. 

This significantly reduces my turnover time and expense.

This will reduce the number of inquiries you actually authorize. 

The entire net profit would then be applied to the HELOC thereby reducing the outstanding balance and further reducing our monthly payment.  

Are there any clever and LEGAL ways to reduce the tax bill that you would recommend?

On paper it's a great way to reduce overhead and drive the bottom line (as long as you're not holding too large of a note).

I have a Navy Federal Credit Union and Pentagon Federal Credit Union credit card.  They both seem to run the same yearly reocurring balance transfer promotions from 0-4.99% interest with no balance transfer fees for 1...