How much?
From experience, you have to see them in person before you get excited about it. In fact, don't even let yourself get over excited when going to see it cause you'll end up buying a POS that you felt was the only option. Trust me, no one is going to list off exactly what is wrong with the car. I've seen ones that had interior trim falling off, cracked paint, cracked dash, dents.. and they said nothing about that. You will know when it's the right car.
And like LT1MAN said, DRIVE THE **** OUT OF IT! The very first camaro I looked at must of been running on 5 cylinders.
I had been looking for an LT1 M6 in earnest the first half of 2006. My budget was $4000 and was beginning to loose hope that that I would get one near that amount, since I was having problems finding any good ones for less than $4500.
I came across a good number of automatics, but the M6s were going for more. Persistence paid off and I found a bone stock '95 Formula M6 with 137k miles in great shape and I got it for $4200. Issues with it are AC does not work, power antenna was broken, the console door hinge was cracked and it had an oil leak (the intake manifold, which I learned is quite common and fixable, thanks to this board). Otherwise, it's in amazingly good shape, considering it's age and miles. Paint is great, no rips in the interior, burns no oil, t-tops don't leak and no rust.
In my searching, I had to figure out if I was willing to commit to a car sight unseen, like through eBay, and came to the conclusion that I was not. As Ralls advises, there is no substitute for driving the car yourself and talking to the seller. In my case, the seller was really the clincher for me. He was the second owner and had every receipt for every maintenance and repair job that he had done to the car since 2000 and he was very open about all issues with the car.
Other cars I made offers on were a '96 Z28 M6 with 136k miles that sold for $4500 and a '94 Z28 M6 with 99k miles that sold for $4800.
Bottom line is determining what you are willing to deal with. I knew that with my budget, I was going to get a high mileage car, but I wanted one that did not come with issues that were beyond my ability to fix without laying out significant additional $$$.



