Low 70's is fine for most ales, it's not ideal but it won't casue too many off flavors, what most of us do is what we call around here a "swamp cooler."
It works surprisingly well. I can get the temps down to the mid to high 50's during the most crucial first 12 hours of fermentation, and that is without a fan. The t-sirts act as a wick to bring the ice water up and around the fermenter to bath it in cool water which will evaporate (especially with a fan blowing on it.)
You can even do what people who used to hand crank ice-cream did, and add rock salt to the ice bottle water bath.
Some guy here over the weekend posted one where he added a layer of insulated foam board around his, and I know of another poster who took 2 of those tubs (you can even get them at "dollar stores" for 5 bucks) Put one inside the other and filled the gap between with spray on foam insulation....Some put their fermenters in the batch tub even...
So there's plenty of options that don't have to cost big bucks....People have been making beer for millennia before the invention of AC and ronco controllers (though a lot of people seem to forget that on occasion.)
Hell, evidently my Uncle, (the black sheep of the family) during prohibition in west virginia used to keep his cool in the "crick" out back behind the police station....Except he wasn't making it "for personal consumption," if you get my drift.
