I am in the works of doing something similar, but at a greater distance than 50 feet. You should be able to buy the home for about half of its original price. I am looking into a single wide because it is MUCH less to move and anchor. I will use mine as a rental but will also consider selling for a certain price.
PROBLEMS: your septic could be a HUGE problem. If you have city septic and don't have to deal with your own system it my not be much of a problem but if you have your own system you may be in for a world of hurt. Buy the time you redo what ever type of foundation you use, re do your utilities, redo your drive way if you are moving 500 feet or 50 miles won't be that much different.
It won't be any harder to sell it, unless it gets damaged, but you would have to either stand to make alot of profit or have some other significant reason to justify the cost of moving the home.
Another poster said manufactured homes deprecate but regular homes don't. That is not true, almost all structures depreciate. An area may go up in value as time passes (they usually do) and that is what cause the apparition, not the home its self. An older home in the same area as a new home will still sell for less unless it is truly unique of special. This is also true for manufactured homes IF they were mostly manufactured homes in the area and land wasn't available (but don't bet on it).
As far as finding a lender; if mobile homes are popular in your area and you meet the banks requirements, both for yourself and for the home, you will have no problems. If those types of homes aren't popular where you live there will be no reason for the banks to compete and they will make it more expensive and harder to get down.