Babe, depends on where you live. Around here (in MD) you can find a cheap place to board (~$200), however those cheap places usually don't take help in exchange for the board (plus you indeed get what you pay for meaning you have 20-30 horses in one field, no barn, no arena, etc.). The nicer places of course cost more (and the closer you are to DC the higher the price). So may be waiting for 10 months is not such a bad idea. You can look into taking lessons in exchange for barn work during those months.
As for monthly cost it's not all THAT expensive to feed the horse in your own place, but you also have to add vet (shots, coggins), dentist, farrier (every 6-8 weeks), dewormer, etc. (plus maintenance of the fields and fence if you have own place). So these all add up pretty good when you count all expenses. Again the amount really depends on where you live.