I've attached a reference book on how to build a modular home. For those reading this, the difference between a modular home, stick built, pre-fab and mobile home is:
Modular home: modules are built indoors and then constructed at the site by placing one modular piece on top or beside the other. It's almost like a construction loan however, the majority of the construction is done inside the warehouse. Most people will have a large deposit paid to the General Contractor and then after completion, obtain a loan to pay him/her off. Wells Fargo is well known for these as are most credit unions.
Stick built: Built on site and exposed to the elements of the weather. If you are building a custom home, construction to permanent (CP) loans are the way to go, however, up to 40% is required as a down payment. Regions Bank, Wells Fargo, Chase, and a host of other lenders can do CP loans.
Mobile Homes are built indoors in halves or thirds. They are sent to a location and placed on the ground. Mobile homes come with wheels and in order to receive financing, must be anchored into the ground and the wheels must be removed. The Mobile Home is then attached at the top and sides of the structure using rivets. Mobile Homes can be single, double or triple wide. Mobile Homes on wheels are treated like a car and has a tag registration on it. Mobile Homes, unlike modular homes cannot be stacked on one another. That only happens when tornadoes are present. Wells Fargo and FHA are still doing these loans.
Pre-Fabricated homes are built indoors. Unlike a mobile home, it is not split in two. Also know as PreFab, one single layer of felt is placed on the roof line across the entire structure. On top of the felt, plywood is placed before adding the tar paper and shingles. The felt keeps the heat and moisture out of the home. Because it is not split in two, the structure is more sound when hit with high winds. The home is then delivered to the site and anchored in. There are no wheels. Financing is usually found at the place where the home is built.
Here's another site: homebuying.about.com/cs/modulareducation/a/modular_homes.htm