My property is located in a C+/B- neighborhood has the following landmarks nearby: -1.5 miles from a major university with a popular D1 NCAA college basketball team-1.5 miles from a children's museum-1.5 miles from an art and nature museum-1.5 miles from a beautiful nature parkIt's the dead of winter, and I'm wondering who I can market and how I can best market my property to on Airbnb. 

With your background in lease management and site selection, that could be a natural next step.Regarding STRs, I can understand the hesitation—accurate expense tracking is critical, and not having that data can make evaluating deals frustrating.

It has solar power, a compost toilet, and other things of that nature to be self-sustaining.

I've included an example below to help illustrate this.So different lenders have different rates (which do vary even for DSCR loans) but these are factors they all consider.See example below:DSCR < 1Principal + Interest = $1,700Taxes = $350, Insurance = $100, Association Dues = $50Total PITIA = $2200Rent = $2000DSCR = Rent/PITIA = 2000/2200 = 0.91Since the DSCR is 0.91, we know the expenses are greater than the income of the property.DSCR >1Principal + Interest = $1,500Taxes = $250, Insurance = $100, Association Dues = $25Total PITIA = $1875 Rent = $2300DSCR = Rent/PITIA = 2300/1875 = 1.23If a purchase, you also generally need reserves / savings to show you have 3-6 month payments of PITIA (principal / interest (mortgage payment), property taxes and insurance and HOA (if applicable).

Heating costs go up in winter, as does electricity due to the reduced natural light and more people indoors.

Because of the nature of a tax lien, it would be difficult to obtain financing from a commercial lender secured by the tax lien itself.  

They pay for themselves and put money in my pocket to build up a reserve for the next purchase.

If OP can lever-up while maintaining adequate reserves, he will be in better position than buying with heavy cash position.  

For the first few reservations, I would put a lot of focus on bringing in good 5-star reviews.

Reason is a Heloc generally carries a higher rate on a shorter term and "Can Never" be used as an "Asset, or for PITI reserves" which are both required when you buy an investment property.