Mobile/Manufactured Homes are valued differently than stick built homes. It is like a used car, once a new one is purchased, the value of the home goes down immediately. If buying a property that sits on it's
own land and the home has been put onto a foundation, then the home & land's value can be calculated like it is a stick built home. If it sits on it's own land, but not on a permanent foundation, then find the value of the land through the normal real estate comps procedures, and find the value of the home's "blue book value" and add together. (MHVillage has a book value report for mobile/manufactured homes for $14.95 each. It will give you a base value, and then the opportunity to add to that value with options - new roof, new appliances, etc).
The third option is where the home is in a park/community. Besides the mhvillage value, the community it is located in, plays a part in what you can ask for the home. I have found, apples to apples, when in a park that has lower lot rent, can ask more for the same home. For example, in my area, there is a community were the lot rent is over $1000/month, and there are so many homes for sale (because the retirees don't want to pay that much), the median home will sell for $25K. Taking that same home and plop it in a community where the lot rent is $600/month, the median home will sell for $60K.
It's all in buying for the right price. Also, many communities will not allow rentals & must be owner occupied.
If you do not own the community, it can be a very difficult venture. Also, all communities require, background check and income/credit verification to be approved for buyer's to live in the park and purchase a home. (Which also means you have to go through this process to purchase a home as well). Also note, if the home needs new roof and/or sub-floor, you may end up putting too much into the home to make a profit on the sell-end. Also, if selling a home in a community, where you do not own the land, you have to get a used mobile home broker's license, or be an agent with a broker that has this license (similar to a used car dealership license).