Half slab, half Basement?

[Jessie]

My darling husband and I are considering buying a doublewide that has stairs/basement an option. A basement 70x30 is not only pretty expensive, it is HUGE, and we don't really need all that space. Has anyone done/does anyone think it feasible to build a basement, half the size, with a slab for the balance of the length?

We realize we will have to have the placement right for the stairs, and that the top of the basement/slab height will differ, because of needing space between the slab/bottom of unit.

Thanks for any input anyone might have...