Best way to finance a mobile home purchase

I'm interested in making an offer on my first investment home. It's a mobile unit on a third acre of land in a nice community of normal stick built homes. I have no experience with these and I was taken by surprise trying to obtain a mortgage for this purchase. Other than 21stmortgage.com, I haven't found anyone who will finance a mobile unless I plan on living in it. I'd like to buy for rental income. The terms at 21st mortgage are hefty and I'm hoping there are alternatives. Thanks in advance for your help.