I'm not an expert on modular homes, but it is my understanding that they come ready to move you personal things into and start living. As far as having it only partly finished by the manufacturer, I think it will end up costing you much more. Some of the reasons modular homes can be sold for such modest amounts are that the manufacturer buys in volume far below what you would pay, they construct them basically on an assembly line which is far faster then you could do it. If you've ever remodelled a house, you know that a construction company can build a complete home from scratch while you're still trying to figure out how to work around existing construction. In other words, in my opinion, you'd be defeating the purpose of a modular home.