Only one additional point:  if you make exception for this tenant's request, you can open yourself to all sorts of possible discrimination claims from other tenants."

It costs less than $500 to start an LLC and about $1,500 annual for LLC tax returns.It should save you a good amount of coin in the long run and provide an additional layer of liability protection. 

Should I ask for a reduction in price or just walk away? 

Since we have additional cash to put the required down payment on a conventional loan I'm inclined to go that way and avoid collatoralizing our primary residence but can someone help me understand the key differences between HELOC and HEIL and why I might be wrong in choosing a conventional loan over the existing equity options?

Among the benefits of this are:1) you can claim the deduction even if you do not itemize your tax deductions2) it can lower your AGI, which may make you eligible to claim additional tax deductions or credits

I think the best way to evaluate an additional investment is "Return On Investment".  

Retire , additional income , ?

There is an additional acre of land that can be subdivided and sold off that was once part of the original farmland about 200 years ago.

There does not appear to be room for reduction in operating expenses.I am doing my own due diligence but would also like feedback from others in the local area as to what they think of the location, the property and prospects continued growth in the area and for increasing rents.

There does not appear to be room for reduction in operating expenses.I am doing my own due diligence but would also like feedback from others in the local area as to what they think of the location, the property and prospects continued growth in the area and for increasing rents.