The post above this one is exactly right. The most important part of the whole process is weather or not you actually own the land. If it's deeded (Indian or BLM land) you cannot take a mortgage on it. However if you DO own the land you can take a mortgage out, but also as mentioned above the coach will have to be appraised and it better be in good condtion, b/c banks are pretty specific about that stuff.
That being said, if you are talking about the area I think you are talking about, I would bet that the land there is owned by the Indians, is it around Villa Shores?
Either way, good luck with the whole thing, that is the section of river where my place is, it's really nice.