Coming from the GC side, what's the piece of multifamily development I'm most likely to underestimate?

Ten percent on hard costs is real money but it can get wiped out by a quarter of extra carry. I've been running spreadsheets on small deals for months and the number that moves my output most isn't cost per square foot, it's the interest rate on the construction loan and how long you carry it before units start paying rent. A 24 unit project at, say, 5 million in debt costs you meaningful money every month you sit unleased.

What I'd trade for your construction knowledge is the exit cap rate question. Value gets set by net operating income divided by cap rate at the end, and I still can't get comfortable guessing a cap rate three years out.

Your cost advantage is real, just not where you think. The place a GC background actually pays is in not getting sandbagged on change orders and in knowing which subs will still be standing at month fourteen. Lenders also like a sponsor who can defend a budget line by line.

But yes, the assumption is wrong on its own. Land basis and financing cost swamp construction savings in most deals I've looked at. If you overpay 400k for a site, ten percent off a 4 million build gets you back to even and you've done all that extra work for nothing.

Also worth knowing: lenders will usually want a fixed price contract from a third party GC, or a very good reason why you self-performing is acceptable. That surprises people from your side of the business.