Egads! Don't do this. Fifteen years from now, when you move out there, house will need to be completely re-roofed and utilities updated. Meanwhile, if you've read MMM's opinion on having a cottage, you will now have two households needing appliances, furniture, linens, lawnmower, automobile, etc.
Since your husband isn't a native, it may be difficult for him to get a work permit with you still in the States.
Plus, there is the old husband's saying that two women under one roof do not make for the best of times.
Better: You and your husband move into that smaller, cheaper apartment now to free up some cash. Also, contact your MIL's church about any retirement communities they may be associated with.
Once you do move out there, a separate little cottage called the MIL's room -- either in the back yard or attached to the side of the house -- generally works a lot better. You can always rent it out later.