There is another option similar to this one that is called Owner completion. With this option E&L Builders does everything from excavation, foundation and setting the house, the homeowner completes the project from an agreed upon point that could be as simple as painting to as complex as running the trades for electrical, plumbing and HVAC.
The choice is you as to how involved you are with building your new home.
Set day is just to give you an idea as to what is involved with setting your new modular home on your foundation.