Sounds like a flat fee with payments and possibly incentives (bonuses) per milestones would be a good fit for you.

You will still need a down-payment (probably 10%-35% of the purchase), you will still need loan closing costs (say $6K-8K), you will still need money to carry the loan until you can exit the loan, you may still need money to rehab (at least to the first draw milestone) if you are rehabbing and you still need money for contingency in case things not quite as planned.Hope this helps. 

.), then you establish the criteria from these "parts" ( I refer to them as "milestones"), then you match the "milestones" criterias to the Markets where the profiles of the properties in that/those market(s) match the criteria from the milestones (at that time in your plan's timeline). 

.- Is the rehab paid in arrears at each milestone or up front?

Offer to pay them out on day 1 or 2 when they hit a milestone goal.  

. $10k is an early milestone.

The scope of work should specify milestones for work approval by you before any monies can be transferred. 

“While millennials share many similar traits with prior generations, they have been marked by a delay in major life milestones, including starting a family and purchasing a home,” said Ratiu.

They are cumulative as the end goal, and broken down into a series of Milestones, by reverse engineering from that end goal. 

My first major milestone is to generate 4,000 in passive income using long term holds so my husband can quit his W2 job.