I'm finalizing my brew fridge aetup now. I started with a new ~10 cu. ft. standing fridge, added a bulkhead fitting, 3 gas line manifold and various sized CO2 tanks, along wit 2.5 and 3 gallon kegs. I probably could have just gone with 5 gallon kegs, but then I'd have less recipes on tap. I also have room for several bottles of brew next to the keg on the shelf.
I do plan to setup a keezer once I move, and keep the brew fridge online too. Not 100% sure of the time frame there though. Still, having tree brews on tap is pretty sweet. Plus I could carbonate/serve a fourth keg without too much more effort. Just need to finish off the bottles in that fridge first.
I would recommend installing a bulkhead fitting in the fridge/freezer so that you can have the gas tank outside of it. It gives you more room for kegs.
I would also advise against carbonating a keg with sugar. Purge the O2 from the top of the keg (should be easy to do), place it in the keezer/kegorator and put it at serving psi (and twmp) for 1-2 weeks. If you want to carb more kegs, and store them (basement would be a good idea/place) you can after they are carbonated. Just be sure to give them enough time to chill down again before putting them back on gas, and ten serving. IF you carb a keg wit sugar you will increase the sediment in the keg. Part of the attraction of kegging is the very limited amount of sediment you get.
I've been kegging the first half of my brews (last three batches going into keg and bottles) so the clearer parts of the batches are being kegged. In theory, this should result in less sediment in the kegs. We shall see, soon, how that holds up.