You have no way of knowing what arrangements or payments the borrower made.  

As others have suggested, attend a local REIA meeting, network with other investors and see if they have any contractors who are accustomed to this type of arrangement who they might recommend.

Just thought I'd share an arrangement I came up with that my great tenants agreed to in exchange for letting them out of their leas a month early:Background - They are great tenants. 6 years.

Are there standard LLC Agreements covering this sort of arrangement?  

We will have to discuss more what we want to get out of our arrangement.

The IRS issued technical guidance detailing these items in Notice 2017-64.Highlights of Changes for 2018The contribution limit for employees who participate in 401(k), 403(b), most 457 plans, and the federal government’s Thrift Savings Plan is increased from $18,000 to $18,500.The income ranges for determining eligibility to make deductible contributions to traditional Individual Retirement Arrangements (IRAs), to contribute to Roth IRAs and to claim the saver’s credit all increased for 2018.Taxpayers can deduct contributions to a traditional IRA if they meet certain conditions.

Let me know if I can help arrange anything.

I contact them the month before the lease expires and make arrangements as to when the unit will be ready. 

If you take the time to screen your tenants properly it can be a very favorable arrangement for everyone.

_______________________________________Just thinking out loud here, but would love to have some dialogue with others about this concept that's been rolling around in my head: Your quote above got me thinking...so many architects (and designers) work with clients/developers with a fixed fee arrangement.