I tech at $20/hour for the arcade I work at, but that's half my going rate for general electronics repair because I get lots of regular hours. Plus I just wanna see the arcade succeed.

As for pulling machines offsite, depends on the nature of the problem - also depends on the bar's opening hours. Most pinball stuff, you keep it waxed, keep on top of cleanings etc, you won't often have something go down so bad you need to pull it off the floor. Spare boardsets can be swapped in and out while you're fixing the ones that go bad.

Monitor stuff, if you're talking about classic videos, beyond trivial adjustments, I don't like to do while the place is open with people rubbernecking all around. Too many things going on around you to take your time and be safe. I'd pull videos off the floor if they've got monitor problems.

As for hours... how long is a piece of string. Are these games all shipshape, have they been taken care of, or are they gonna give you constant problems? How often will you have to go on a hunt for an unobtainium part? Is the owner buying games with monitors that are well-supported by a community of people who know what they're doing, or is he importing some crazy obscure Japanese nuttiness for which you can't get parts anymore and the scanned-from-the-manual-at-too-low-resolution-and-translated-by-Some-Guy schematics have a big gap down the middle and in place of the missing information there's an obscene limerick about a technician who somehow gets his penis caught in his multimeter while measuring a 20k flyback line?

(if that seemed AWFULLY specific, there's a reason for that, and if someone is reading this now and going "Oh, you're working on an MS2931 too?" Well... you have my sympathies)

So, yeah. Hours will be impossible to tell until you see the state of the equipment, and figure out what's likely to go wrong and what's likely to stay right. Good luck.