I take it you mean besides camping?
Are you going to Delancey or Big Scrub?
Camping is your cheapest alternative....(Although, this time of the year it's no good because of the heat).
There are a couple of cheap places depending on which end of the forest you are staying at.
This is about 15 minutes from the forest in Astor.
http://www.vrbo.com/31528 it's 85 bucks a night.
Which way are you coming from?
You can also send GrizzlyBear a PM...he know's that area really well. He'd probably be able to give you a good deal of help.
