I have a smallish SUV and @David Ross has a compact car.

Compact flourescent lightingSolar powered outside light fixturesCedar wood for studs, decks, joists, etc.

My thinking is that, if he completes the project on time and on budget, then he would receive a commission as a proportion of our profit (my thinking was 10% of profit).

If you have long-term rentals, the most common misconceptions are generally around properly calculating depreciation (proportioning the value for improvements vs. the land, which isn't depreciated, and also including applicable closing costs in the depreciation/amortization). 

Statistically, the defalt rates are inversely proportional to the amount someone injects into a deal. 

It's really just a general rule about ratios and proportionality: If A/B = C/D then (A-C)/(B-D) = A/B = C/D. 

Thanks for the comments @GeraldGrinter and @ScottEgbert the concern may be in direct proportion to the equity one holds in their investments? 

So expenses will be a little higher proportionally for rent. 

I'd guess that's all zilpy does.Now, where to get it in a nice compact format, I don't know.

Profits will be returned proportionally to the investors.