I want to be sure you are clear on an FHA loan for a 3-4 unit. FHA requires that a 3 or 4 unit property be self sufficient. On top of that, you can only use 75% of the estimated gross rents as determined by an appraiser (although you do get use the estimated rents for the unit you would owner occupy). In other words, if the property makes 4,000 in estimated gross rents (1,000 per unit), we could use only 3,000 as the estimated rents. If your mortgage payment is 3,100 (including taxes, insurance, MI, any HOA dues, etc), that property will not qualify for FHA because the payment is greater than qualifying rents. I have never been able to qualify anyone on a 3-4 unit for FHA on the west coast, but I'm sure in some markets it would work.
While on the topic of loan programs, it's important to know that just because FHA (or other investor) says you can do a loan with XYZ characteristic, doesn't mean every lender does. Lenders have what are called "overlays" and they are basically stricter internal guidelines that have to be met. While one bank will do a loan with a 580 credit score, another may have an overlay that their minimum credit score is 620. One may finance mobile homes with FHA while another will not. One may do the construction 203k or Homestyle or portfolio construction loans/rehab loans, others may not.
Also, you mentioned several times about lenders in Maine. Many companies, especially the ones that could help you with alternative loan programs, are licenced in multiple states or nationwide and US territories. I wouldn't necessarily narrow down your lender search to the person you like best in the area you are looking at. There are SO MANY lenders nationwide to choose from(though in this market, the ones that were in it for the easy refinance boom money will be leaving any time now). I want to also add, that before taking the plunge, I would recommend using a company associated with a bank. While all of us in lending are taking a beating with the interest rates as they are, the ones not associated with a bank have a greater chance of not being there the day you need to close because they don't have the balance sheet diversification to continue business.
AND...(I feel like I keep talking), I remember doing a loan very similiar to yours with someone who lived in the UK. I don't remember the card she had, but it was a Visa/Mastercard/AMEX- one of the big ones here in the states. We were able to order an international credit supplement from them to add to her credit history. Do you have one of these that could help?
I am personally on the "rent for six months to a year to get your bearings" train. Imagine how horrible it would be to buy a property you later find out is in an area is completely not your style, especially given the differences in weather. Experience a Maine winter first!
Good luck and let me know if you have any questions about my rambling response!