I'm working on a deal right now that could be a 40 house development... or it could be nothing. Why? Because the infrastructure doesn't exist to support the development, and it could be as much as $2MM to put in the infrastructure (think street and sewer), and because of setbacks, etc, it could be down to as few as 20 houses without some kind of variance. And that's before the cost of the land and the cost of the construction, all of which would rest on the shoulders of the developer. Shoes, a car, etc an assembly line can be configured and stamp out near identical products year after year. Even if you intend to build generic tract houses (like this development would be...), you still have tremendous up front costs and "tooling" and the variation of each new development -- location, elevation, access to services, etc.