This is seeming to be not such a simple task. Next someone will say I should get a brush to clear off rust/debris, and then some sort of grease before re-applying the nuts? 
My understanding is that if I get the set for $99 at CT (for example), I could hoist one side of the car at a time, put the two jack stands in place, and then do the other side so I'm not doing 4 separate hoists (just two) per vehicle.
I didn't know that I needed a separate wrench ("breaker bar"?) to remove the nuts - but I am reading more and more to not use the torque wrench to do it - why is that -- to protect the other wrench?
And yes, I figured out that I'd need two sockets, which isn't a big cost.
Let me rephrase:
What items will I need to do the changeovers with relative ease and without breaking the bank.
Changeovers will likely be free on both the Mazda and the RX - just the Forester at $80/year. The purpose of the DIY is to avoid the hassle of having to book appointments, drop off the cars, pick them up, etc. The $ savings are only relevant if I'm not spending as much to buy the equipment and then doing the work myself.
It looks like in the torque wrench, breaker bar, and sockets, I'll be spending $97 (amazon), and then another $80-$100 for the lift and stands (unless I buy separate things for 2 ton instead of 3 ton). Somehow, I'm at $200 and I have to do the work myself. 
At this point, it looks like it'll take 2 years to pay off (assuming nothing breaks) from a strictly financial standpoint.
Most cars don't have a jacking point to lift the whole side, smaller cars yes, the SUV, probably not. Sometimes it's easier to go front/rear than side to side, providing you have proper jacking points.
You don't really need anything more than what came with the car to change wheels, it just makes the job easier when you're doing it to have the tools. As mentioned, you don't really need jackstands to change wheels, as long as you're not sticking your bits under the car you won't use them. You don't really need a torque wrench if you have a good idea about how much torque you are applying, but as you have no experience, well, get a torque wrench.
Not using it to remove nuts is indeed to protect it, a click type should also only be used in the range before the click, tightening more after the click can damage the calibration. When removing nuts nobody remembers to dial up the torque setting and it clicks immediately, you loosen the nuts, now it's out of calibration. That's why it's a good idea to only use it for the actual final torque setting.
Buy tools on sale, never pay full price unless you really need it. Most hand tools go on sale for 50% off at some point.
