I have one 1900 house with 5 bedrooms and the best HVAC solution is 2 mini split systems and a furnace/central air system for the half of one floor with an accessible crawl space to add duct work. 

Until then, I'd like to pick up and learn what my options are here for a creative solution.

On the plus side, the QBI deduction in the recent tax bill will save you some coin.You should have SOME type of corporate veil (move it to a corporation) to protect your personal assets as well as create barriers between the properties where necessary, but the specific solution to your situation is a bit too vague for anything other than generalizations without more clarifying information, and your best and most specific advice will come from a local and trusted tax advisor and/or lawyer. 

It seems like he is not exempt from capital gains tax so trying to find what would be the best solution to this.My questions are:1.

You need to negotiate with them to find a solution. 

HELOC might be a solution for taking funds out.

If the transaction is completed and recorded, there may be some documents signed at closing where both you and buyer agree to fix any errors, although I believe it's usually reserved for a missing initial or something, but may be a solution if both parties understand and agree a mistake was made. 

These clean grout lines can create a modern, contemporary, and high-end aesthetic. 4.

No landlord should tell you they have money problems and YOU are the solution to the problems.

The best solution at this point is to "fix" your ability to get loans.