It sounds like you / your parents should just hire a professional property manager for the inherited properties.  

Her and her husband are getting older so they hired us to manage. 

You can also let a tenant pay the lien/encumbrance off.I can swap a lien I payoff for an interest in title.Material and workmen's liens can be financed at full face value after being purchased at a discount by a clean-up contractor (one hired to complete unfinished work). 

Our house down there is the same way, with a metal roof, open air, then a concrete floor or roof above our 2nd floor living quarters. 

If you just hire the cheapest or first PMC you speak with and it turns into a bad experience, please don’t assume ALL PMC’s are bad and start trashing PMC’s in general.

I'm sure there are many more experiences where the contractor hasn't fulfilled their scope of work and gotten away with rushing the project to meet the deadline, And, I don't want to be as naive to say that I'm that 1% who can have complete quality/operational control, but I'm confident I can establish a system and hire independent inspectors to review the contractor's work. 

@Michael Plaks comments in this recent post on making sure the person you hire understands real estate sounds really relevant to your situation.  

Determine the cost of construction (hiring a contractor in the GNO area is going to start around $165-175/sqft to build) and be sure to include all holding costs, as well as interest in the loan.

(that is, assuming you've hired an agent with experience, market knowledge, and the wisdom to be able to guide you to what you're looking for). 

You'll probably get better service approaching it that way than hiring a professional manager anyway.