Just another thing to consider. My husband and I were looking at a higher end modular as a guest house AKA MY SEWING ROOM and found out that there were some financing issues not only now but down the road. At least in this area, mobile homes are specialty loans and are usually not handled by traditional banks - there are lenders who do work with the dealers and money is available, just not from regular banks.
That was okay with us since we would not have needed the financing for long. BUT, it can negatively affect the ability of a subsequent buyer to obtain financing... Someone told us that one mobile/modular home had to be torn down in order to get standard financing on a property they wished to purchase. We decided to hold off and go for stick built.
Laws and zoning differ from place to place, but I'd sure check out the rules in your desired location, even if you are not planning on financing.