Without knowing the specifics of the home you have in mind, as well as the layout of the basement you have in mind, as well as the site-specifics such as the ground snow load and frost depth, it would be hard for me to give any information and I deal with foundations on a daily basis in my work in the modular industry.

I would have an local engineer of architect spend a few hours designing one for you. You're main concern will be headers of any doors and windows in the basement and supporting a center girder down the middle, in the case of a double-wide.

I can say that it is a great way to expand your storage and utility space, as well as opening up some additional living space.

Wayne