With any designer, ask how many homes the firm has built and how many are in the pipeline, and arrange to visit a finished house. The growing prefab field has led many designers to jump in, but not all them actually have designs that have been built.
Also ask what changes can be made to plans and how complete the house is when it arrives from the factory, a variable that can affect construction time. Some modular houses arrive 90 percent finished, with light fixtures in place; others need considerably more work from a contractor.