My experience indicates that solid due diligence upfront on the economics is the critical factor, the tax aspects often take care of themselves with only modest planning.

I was shown about a handful of their holdings in the Houston, Memphis, and Little Rock markets, but the cash flow and CoC returns were less than $100 per month and 2-4% after factoring in additional expenses like 7% vacancy and 10% maintenance per month to go along with 20% down and conventional mortgage.

Rising home prices for developers isn't new, but if you were in contract, what they did is most likely illegal.

Please be aware that all national homebuilders, and I would assume solar developers as well, will want enough time in the contract to conduct substantial due diligence, rezone (if needed), and get all required land development permits in place before closing on the land. 

The loan amount will typically be determined by appraisal (LTV - loan to value ratio) - but your qualification will also be based on other metrics like you mentioned - DSCR ratio, FICO and some other factors. 

Always approach as a developer with a specific usage.  

I'm an investor and flipper in the city, and I work for a developer focused specifically in Lowell as well.

Now you have x% of your original property equity, less cash-out fees and however much you need to pay to service the original loan while you're doing business development. 

So, if a developer comes along and buys the mobile home park you will lose your entire investment.

The city's macroeconomics is looking great - lots of population and job growth due to the booming tech scene and many companies choosing to move and develop here.