A quonset hut could work, too

Since straw bales are out of the question (there aren't going to be any available till after harvest season).

 We could go with Penta treated old power poles in either cabin or timber frame option.
This one at CL would really be within the budget. Plus i wouldn't have to worry about load carrying supports.

Of course we have to see what kind of room we have under the oak trees first, and that'll have to wait until the tenant is out at the end of the month.