OKay so when you buy an APU, does it come equipped with AC or do you have to buy that extra?

The answer is "yes". APU usually translates to Auxiliary Power Unit. To me, that means a standalone unit that just generates electricity. You add on the A/C. Some sellers however advertise units with an engine, alternator and A/C as an "APU".

some APU's, like the tripac, have the AC compressor right on the unit.

Not a huge fan of that IMO because the a/c lines need to be run up to the bunk, and that bunk moves more then the rest of the truck does.

Some come with an A/C and some do not but if it's for a truck specifically then most the A/C.