Based on my recent experience, it is a large market. Ultimately, my own bank took mine.
Depending on whether you are looking to finance new or used, and if new, the price point, the thresholds for the good loans and rates will change. If you have perfect credit, options are easy to come by. If not, they number of lenders decreases and the rates increase. It is not much different than financing anything else.
Being already established with a financial institution is helpful, and many of the national organizations, i.e. Escapees, etc. have relationships with financial institutions that can be worth looking into.
Financing an RV is basically a financial commodity and it requires some patience and diligence to find what works best for you. They are out there, and they all do it just a little differently. One size does not fit all here.
Good luck!
Kim