I itemize my repair costs and charge my tenants accordingly.This all spelled out to them in my tenant handbook that they receive prior to leasing from me.

If you own the lots, and you can get the house 60% built - meaning it is dried-in (correct my spelling or misuse of this term, as needed) - then you might be able to go a local hard money lender and do a cash out refi to finish the project. 

In your operating agreement you would spell out the responsibilities and payout structure.

He or she will probably come up with a few more "scenarios" that will need to be spelled out. 

In your operating agreement you can spell out how the profits/losses are split.

Spell out exactly what you are allowing them to do, what materials/colors will be used, who will pay for materials, whether you will reimburse them for labor, etc.

I am wanting to create an additional term in the purchase agreement that spells this out. 

You should have a written agreement spelling how you will operate including covering contingencies of “what-ifs.”  

In CA, the good neighbor act spells out that property line fencing is to be shared equally between neighbors for maintenance, repairs, and construction of new fencing if the fence is to be on the property line (the shared line).

@Matt Clark Lexington doesn't have an affadavit form to spell it out..but I looked at the Roanoke one with the assumption that Lexington's model would be similar...this is what it says under the contractor license exemption section:------------------------------------------------------------------I am 1) the owner/landlord of a residential rental property or am directly employed by (not acontractor for) the owner/landlord performing work on my property, AND 2) if I am paying anyone toassist me, those individuals are licensed contractors*, AND 3) this work does not involve initiallyestablishing/constructing the rental unit.