I was in the same delima last year. I picked up an old freezer last year to use for fermenting beer. I had to make a new top from Styrofoam to give me enough internal height for an airlock.
The setup worked really well last summer with garage temps in the mid 90's. My beer stayed at a nice 65F while fermenting. Moisture can bee an issue, but mopping up the condensation from the walls regularly helps a lot. I let it sit for a few days with the lid off after bottling day so that it has a chance to dry out and I clean the inside with bleach and water on brew day. This usually keeps anything nasty from growing.
I use a mechanical controller to keep the temp in range, and a small fan to circulate the air inside the freezer. A small 5 dollar digital outdoor thermometer is used to check on the Temp.
I should be able make a nice Lager with this setup, but I have yet to try it.