We don't pay rent either, the Rainbows pay £20/term (so £60/year). Half of that goes in the bank for census, which has been knocking on £30 for the last few years (LaSER). We don't pay rent, and work on about £10/week for activities, with at least 2 or 3 nights per term "free", which gives us enough to cover badge costs etc.
We were lucky that when I took over 5 years ago we had just under £1000 in the bank I've spent it all now though which has meant we've been able to buy a flag, subsidise subs for one or two, trips and pay leader training and uniform without any bother. We also have a healthy amount of 2nd hand uniform that girls leaving have donated, it's available to any new starters in return for a small donation to unit funds - we suggest a fiver donation for a full uniform but it's at the discretion of the parent.