There are only a few lenders doing loans on manufactured homes, and FHA and VA will do them as they consider manufactured homes as low income housing. That being said, it would be a very difficult property to finance in good lending conditions and since you are considering going the non-owner
occupied route, that makes it virtually impossible. Course the more cash you
bring to the table, the easier it gets.

As mentioned a couple times, an owner contract would be the easiest way to proceed and my guess is that the owner knows this already as at some time he has probably financed it.

As for your $ per square foot calculation on the new house, that seems quite low to me too. Probably $75 per foot is more in line. I'm assuming you want plumbing, electrical including lights, switches and bulbs, and heat.

BTW, log homes aren't much easier to finance then manufactured homes either. M & T Bank is the largest financier of log homes in the country, if you choose that route. Good luck.