Looking to buy a used, 2004 Mazda 3 (Automatic). Need serious, detailed advice.

Hello,

So, I went to go look at a 2004 Mazda 3 yesterday and I right off the bat, I noticed quite a few things appeared to be "seized". To name a few:

-The rear, passenger wheel would not spin (they had to drive forward and backward a few times to get it loose and spinning again).

-They had to use of some type of what read on the can "Air Conditioner Recharge" hooked up to the line to get it working again, but it seemed to only work for 5-10 minutes before the air went back to being warm. Could this mean the AC needs any kind of major or expensive repairs?

-Something seemed wrong relating to shifting gears because he used a screw driver somewhere on the bottom right side of the shifter area but I didn't see what he did.

-There was an intermittent, squeaking type noise in the engine area. He claimed it was because the car has been sitting for a while and the "belt" needed to be replaced. What belt was he referring to?

I couldn't take it for a test drive on the highway because that rear passenger wheel was still heavily resisting movement, I'm guessing due to the brakes on that side being seized or something, but I'm no expert, so I'm not sure.

I'm a student and while he agreed to fix everything while Safety Certifying and E-Testing the car, this car is already a few hundred dollars over my budget and I want to make sure I'm not buying a Lemon or pile of junk. I need something that is reliable and not require any major repairs (at least, not in the foreseeable future).

Like I said, I'm a novice when it comes to car knowledge, so if you could provide me a list of every single thing that is important that I need to inspect before making any decisions, it would be immensely appreciated.

Thanks in advance!