Isaac, I've got some thoughts that I'm going to tally below. Hopefully they make sense and give you some good insight from another investor in Portland. Side note, what neighborhood? I love historic neighborhoods.
1) Some back ground on the numbers would help. My initial thought is what would hard or private $ have cost you for this project? How does that cost compare to the expected returns of your investor? Having other sources of $ gives you more leverage in negotiating these types of deals.
2) Is the investor's 10% a simple interest per annum or flat rate ROI? Structuring this as "simple" interest versus a flat 10% ROI works better if the project is under 12 months. It is in your favor if the project is over 12 months. Just a point I would consider, similar to factoring hard $ points versus interest rate.
3) What's your "overhead" attributed to the project? Insurance, office space rent, phones, workers comp, etc. etc.? This is a very smart line item to build into the "cost" of the project, just as the investor's 10% return is a cost of the project. Good job here.
4) Historical design review is a serious process. Very serious process. I just bought a duplex in Irvington. The seller sold the neighboring 6plex to another investor before my company was ever part of the duplex sale (that investor backed out of the duplex purchase, he was going to purchase that as well). I met the other investor last week. He purchased the 6plex for just over $600K and plans to resell over 1.2mil. His comments. "You can have Irvington, I'm never working here again".I hear that a lot from investors working in historic neighborhoods. The returns are very appealing, but the design review is legitimate. In my experience we would build some sort of management cost into the profit share for the design review process. This is going to be a head against the wall session. Hopefully it will be your architect's head.
5) Project management should be a line item "cost" to the project. Every GC joint venture we have done has included this type of line item, albeit a small one (we want the GC invested, but we also want him to enjoy the project).
6) Did you consult a CPA as to your projected income on the project? Would it be best to remove your company profit from the 40% and take that all as gains? Would it be better to remove your personal gains and take it all as income for the construction company. This may be a minimal consideration, but one thought that came to mind.
7) We have done this same exact profit split where the GC got 40% of profit and we got 60%, with our private $ being a cost to the project, so your split could be considered a "market rate" split.
8) How did you structure ownership? We always own the project and use joint venture agreements. Control is key!
9) Breakdown of some other "profit split" deals we have done locally:
We have done a hand full of investor/contractor projects where we were basically the glue. Our deal, our due diligence, our design, our ownership. But, not our $ and not our construction company. We've partnered with a GC having skin in the game. We paid out net profit equal to the amount of "skin in the game". The GC used private $ as well so our cost of funds were our own private expenses. We have done similar profit shares where the cost of funds was a cost of the project.
Our latest profit share deal is a recent purchase in Wilshire. We approached the investor as a private $ loan. We had our investment packet with all due diligence completed. The packet always includes scope of work, purchase price, appraisal, rehab budget, break down of expenses and an LTV, showing our estimated resale. That out of area investor offered a profit split rather than a straight interest rate. He offered a 70/30 percent split. We get the 70, he gets the 30. In this scenario his simple interest return of 10% was changed to a projected annualized return in the low 20s. Our cost of funds increases and projected profit was reduced, but it was well worth it. The loan has 0 interest so our risk is very low. Also, we are not penalized if the timeline gets extended (something to consider in historical design review). The investor's return is actually a higher cost than hard $. We could have done this deal without him. However, the lower risk on the project and ability to do more in the future persuaded us to go the profit share route.
Hopefully this helps your thought process on your deal. Happy investing.