But is it possible to fix up over 200,000 miles worth of wear and tear? Replacing an engine is one thing, but an entire body? To what extent can a used vehicle get so old and worn that it can't be made like new again?
I'd never buy anything with those miles. Something with 100k, that is a reliable model to begin with, and is in good shape, that would be fine.
When I was shopping for a Tundra 6 years ago, any with 100k miles and in good shape was 2/3 the price of a new one. I figured that wasn't enough of a discount, so bought new. I could sell it now for a lot more than I paid. Makes/models that are cheap used are not necessarily a good deal, though.
I would not take off vagabonding with a car payment, unless you have guaranteed income. Better just to save up, and when you are free, be really free. I saved up as much as I could for 8 years out of school, and then basically lived off the interest for 11 years, and had more $ at the end than the beginning. You may not think $377/mo is am lot, but when I was doing this full time, my total expenses in the 90s were ~$250/mo... for gas, depreciation, repairs, food, entertainment, insurance, even health insurance. In todays money that would be ~$450/mo.
You mentioned wanting an SUV. In the used market I'd suggest looking at Sequoias, as they don't seem to hold their value as much as 4runners, and are a solid vehicle.
Buying new or used, it's a tough time for vehicles right now. Prices are high.