Multiple problems! Overheating, no power steering, air conditioning works sometimes, rattle

The problem is you haven't included any test results that could help identify a diagnostic plan. Every problem you described commonly happens on every brand of car, and they have all different causes and fixes. If you're going to try to tackle all of these things yourself, the first thing I would do is buy a scanner. I use Chrysler's DRB3 scanner because with an extra plug-in card it will do emissions-related stuff on any car brand sold in the U.S. After 1995 up to 2004 - 2007.

The first thing to look at under live data is the actual coolant temperature. Hot-wiring the radiator fan is not a way to fix anything, and no professional would ever do that. There is an electronic relay that controls the fan. Some people complained that when sitting in traffic with the windows open, they could actually hear the fan run, so to address that the engineers got rid of the terribly reliable fan relay and went to an electronic one that slowly ramps the fan speed up and down and runs it no faster than necessary. Electronic components are never as reliable as the simple mechanical devices they replace. If the scanner shows coolant temperature is 210 to 212 degrees, you will see the fan listed as "on". If it's not running at that point, suspect the relay. This scanner will also command the relay to turn on when you select it so testing of the circuit can be done.

You said you spent a lot of money on this car but you didn't say on what. With no history to go on, my first thought is too many random parts were replaced in an attempt to solve various problems. That is the time it is less expensive to get a mechanic involved. Power steering can be fixed, but I need other clues and observations to know where to start. Lots of things can rattle. You didn't say if the car has to be accelerating or if the noise will occur with it standing still and you raise engine speed.