I used to until I got burned for being nice. I shared this over at BYOAC...
If it's not fixed by the time you get there, it's because they don't know how to service their machines. You might clean up a specific issue, but it's an indicator that other problems might be overlooked. Drop your offer and walk away if they stick to the same asking price. Besides, if you fix it, you just increased the value of the machine, and that's a perk that should be meant for you after you've become the owner.
I went to go buy a Ms. Pac-Man when I was fairly new to collecting. A guy wanted $400 for it, but he said it had issues. I went out there with a few fuses, some solder, and my soldering gun. I was unsure of buying a non-working game, but he said he'd let me work on it for an hour or so before taking it home. Well, fast-forward an hour later and I had it working 100% after fixing a few cold joints and replacing the fuses. I pulled the cash to pay him and he said, "Well now that it works all they way I can't let it go for under $800. They go for that on eBay all day."
I stared at him in disbelief and with a dirty shirt and hands. I just spent an hour fixing his machine and he went and jacked up the price. I told him it would be $50 for the fix, and he refused to pay it and said that we didn't have a deal. What an a-hole.
The repair would have been $400, and you would then have to had pull a "Ghostbusters" and say "Oh, well, then let me put it back the way it was for you since it didn't work when I got here."
One thing I have learned in this hobby over the years is that the rule is the guy you're dealing with is probably going to screw you over given the chance and the EXCEPTION is you might get a fair deal.
Always expect the worst and you're never disappointed.
