Lease land and take care of your horses yourself ;)
Try talking to the owner about working for board
Look at renting a pasture and just haul for lessons and shows
Totally depends on what state your in. Some states are more expensive if they have to import hay from other states due to not being able to grow their own. Also does depend on location and type of barn. Show barns are more expensive vr let's say a family run barn.
Work off part of the board if that's an option. Look for rough boarding instead of full or training board, you have to do a little work but it will be cheaper.