The point is, it would depend on each particular property's total solar resource fraction (TSRF), roof age, system cost (initial and lifetime/financing), building function, building lease structure, and system ROI over a specific period of time. 

It was a fraction of the other markets we are in Houston, Phoenix, Dallas, Huntsville.If you buy the right deal sure... but its always nice to invest in the places where the tradewinds are at your back.

I would create a steady marketing campaign with a fraction of the the $20k in order to create more money and more potential deals.

Or paying the tax and joining the syndication.In its purest sense there are syndications set up where you can take title to fractional ownership of real estate itself. 

I also read that a large fraction of tenants are on welfare and struggle to pay rent. 

Put a portion in the stock market via Vanguard Index funds, consider ETF's maybe through such sites as Betterment or others and put some fraction of it into RE.

There are old motels all across the country that can be repurposed into STR units, eco resorts, etc. with a fraction of the risk. 

In other words, if future appreciation is a "do or die" thing that is absolutely necessary for your financial success, then do not buy the property (unless the property is a tiny fraction of you overall net worth...Warren Buffet can afford to take a big 50% loss on a 500k house, but unless you have a huge stack of cash lying around, most beginning investors cannot afford to take a loss on a  property).  

Level of involvement (i.e. active management, passive, very passive such as fractional)3.

These are called fractionalized or multi-beneficiary loans.