Such a horrible loss.Regarding your property, I think as the trends in the report continue over the short term you will be able to sell closer to full value in coming months.

Since you’re considering converting the upper unit into a short-term rental, you may also want to implement strict rules around smoking or strong odors in your house rules to avoid future issues.

Will you use the HELOC as a short-term bridge, or plan to hold it longer?

call a few brokers and just see what their terms are.

I am interested in learning all I can about Long Term and Short Term Rentals. 

Sometimes the long term capital gains are palatable and it may make sense for you to pay the tax rather than force a bad deal.

Read and follow your lease, don't allow your tenant to dictate terms.

Something more passive via a syndication could work for them, and otherwise they'd probably prefer something simple like a long term single family rental. 

My ultimate goal would be to buy fixer-uppers to turn into long-term rentals.

In my mind sub to is for short term .. long term rentals is very problematic for many reasons.