Vacant pads are the least attractive form of upside in the industry. Sellers often market their properties as value-add by quickly filling up lots. There is a reason they didn't capitalize on the 'easy' money.
Moving in homes requires a few things to take place. First, you might need to obtain a dealer license, which can be quite an arduous process. Second, you should decide on new or used homes. Not all communities can support new homes due to appearance and tenant creditworthiness. New homes are backlogged by several months due to demand. Used homes are scarce and usually overpriced once you factor in setup and rehab costs. Then, non-recourse financing is hard to come by. Mobile homes are considered personal property and therefore depreciate. In some loan program, the landowner signs personally to backstop the loan for the tenant.
The solution I see most larger players utilize is a lease-option or rent-to-own program where the operator holds the paper on their books. It isn't perfect but it can expedite the vacant lot fill up process if you have the capital. Another alternative is to partner with a mobile home lender and place the loan with them. While ideal, I've had little success with these types of programs. Not all locations are created equal.
Your mileage may vary.