Some transport companies have house kats that can get off the road and onto the site for an additional charge or you can hire a third party if the access from the road is limited.
While the home needs to be paid for prior to delivery in many cases, the transport companies carry the insurance from the factory to the site. Your builder's risk insurance picks it up from there. You've got to remember the home has already been through numerous inspections prior to delivery, so the time it takes to finish is minimal.
I've got plenty of experience in both site built and mod construction. Also, securing financing is no different than site built unless you're dealing with someone that has no experience originating loans. Mods are built better than most site built. Manufactured homes are in a different classification than a modular. You must know how to differentiate between the two.
It's sad to say, most realtors are clueless to this fact. It should be a requirement to be educated in that space prior to licensure.