The Split Air systems is mainly what we have here in Tokyo, I just checked and for the 500 sq ft area that would be two air cons, they each cost about $600 here and I could install them in your garage in an afternoon. Basically you have to have power inside near where you want the fan unit and then you have a hole in the wall that the power cable, drain and coolant pipes run through, the hold is usually 75mm or 3".
You put the outside unit on level ground, and attach the inside unit above and to one side of the hole, you attach the power cord, drain and two coolant pipe to the inside unit, and you have already attached the mounting plate on the wall, pop the unit onto the mounting plate, it hooks on the top and clicks on the bottom. then outside you hook up the three wires to the outside unit, red/black/white, you hook up the two coolant pipes, and then run the drain somewhere that works for you, tape up the coolant pipes, the drain and the power cord into one unit and attach it to the wall in a few places, make it nice and straight so it looks nice. Then you open the valves on the outside unit to let the coolant flow. Usually they have enough coolant in them for a 5-7 meter (16-22') coolant pipe run. Go inside and plug your AC into the wall outlet, put the batteries into the remocon and you have cool air. The units that I was looking at here are all 200V single phase, for the larger units they usually do the 200V.
Installation here by a pro is about $400 a unit, so I'd say here in Tokyo I could get two units installed that would do your 500 sq ft for about $2000.
The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
William Arthur Ward