Converting Fridge w/ Top Freezer Temp Question

I've been looking for a fridge or freezer on Craig's list lately and I think I'd like to pick up a cheap fridge with a freezer on top. This seems to be the most common type around people are getting rid of. My question is if I control the temperature of the fridge compartment what do you think the temperature of the freezer compartment will be? I've done some browsing on how refrigerators work and can't get a complete answer on what controls the temperature of the two separate compartments. I'm assuming many of you guys on here do this and would love to hear from experience what your temperatures are in the freezer compartment. I'm hoping that the freezer compartment would be reduced to a nice fridge temperature for storing bottles and such. By the way, I brew ales, so the fridge compartment would be anywhere from 60-70 F.

Thanks