Eric,
We had the exact same issue when we bought our property (26+- acres of woods with a tiny house and several out buildings) at the height of the real estate boom. Things are a bit different now, but our issue was the appraisals. Standard real estate appraisals depend on nearby comparable property sales. When your property has no comparison, the mortgage guys balk, and it's only gotten tougher.
Ag Choice is a good start. We used an independent broker who made it work for us and also a few friends with similar properties. If you'd like, send me a private message and I can give you a contact name and number.
For everyone's benefit, what we had to do was a second loan to cover the gap between the appraisal and the purchase price. We've since refinanced and gotten rid of the second loan. Second time around, the same broker found us a lender who didn't ask for an appraisal - not likely today.
Bottom line today, if it doesn't fit the box (i.e., standard development home exactly like 20 others that sold nearby), most lenders won't go there. And those that do will charge a premium rate. Just bare in mind, "premium" rate is still going to be significantly below the historical average.
We're at 4.9% now, and I'd love to refi again to get these sub 4.0 rates, but I just don't think we'd get a lender to bite.