An existing basement won't have the cutouts for the steel chassis of a manufactured home. It would need to be built up a couple of feet to make room for the chassis, so you could get the cutouts then. It won't have the footings for the support poles in the right locations for either a modular or manufactured home, so all the support pole locations would need to be dug out and have proper footings poured. Do the math and see if what you save on not having the foundation poured is lost in modifications to the basement to make it work.

30â wide homes do exist, and you can customize a 48' home to 50 feet, but I would take numerous measurements and verify actual home versus nominal measurements before purchase.