Whats my best solution?

Ok, I am trying to figure out what to do. I have an old fridge that I want to turn into a keg fridge/and use as a place to control fermentation temperatures. Is there a way I can have both? I am planning on buying a temperature controller, but I am not sure if I need a single stage or a two stage? Any thoughts would be great.

A second fridge.

Either you have the controller set for serving temps or fermentation temps.