Builders profit margin in my area is 17%-20%+ if they're financing. It sounds like you're hiring a construction "consultant" who will not be issuing checks etc. Even then someone would want 10% plus in my area and even that doesn't register on the "good deal scale" (too low). What are you going to do for money for the house plans, building permits, engineering permits for septic / sewer connection, tree removal, excavating, septic system installation, foundation, concrete all before you get your first stage payment?
Rule of thumb in my area. You need 10% or more of the cost of total construction cost to cover your subs (unless you can convince them to work for up to a couple months without money) until you get the first stage payment. I'm going through a spec home right now and I have 15% of construction cost in reserve for subs until stage payment. It's the bare minimum and that's using my credit accounts (not accounted for in above 15%) at the lumber yard that will buy me 30 days for the framing, roofing and siding.
The numbers you gave above I wouldn't bet success........BUT I'm pulling for you!!
As for your question does 7% sound legit? In my area if you offered 7% in even 2008 almost every builder would still chuckle, mumble and walk off.... In today's economy? I would assume if he's working for that he's unlicensed and uninsured........
Oh, that's another upfront item. In my area in order for me to build my own house I had to come up with liability insurance $2.3k, builders risk $1.7k, workmans comp. $600 (no employees) and road bond $100.
Oh, another upfront number is energy modeling. That's another $700 deposit. I'm sure you're in an energy zone living that far north.
Good luck but I really think you need to pick the brain of an objective builder in your state with no skin in the game. Even in the dark depths of the last recession no one would work for the numbers you quoted above that was LEGIT..... If you're a real estate agent surely you have worked with a builder before that you could buy them lunch and run your numbers over with them.