Some banks treat motorhomes like expensive cars and only give 6 years and fairly high rates. Others may have loans for 10-15 years and mortgage-like rates. Ditto for credit unions.
We have always used Bank Of America for RV financing - they have a unit that specializes in it. Most dealers can make arrangements for you. BOA has decent rates and does a good job servicing the loan.
You can also Google RV Finance and see a variety of places that specialize in RV Finance, e.g. Essex Credit, Fun-loan.com, etc. I would get some quotes from a few of them as well. Armed with that data, you can usually negotiate rates and terms with some others. And no problem dealing with the online credit brokers either - they handle all the paperwork and make things easy for you.