Re: Going bench rate for Amp techs?
My bench rate is $40...and it's about to go up due to increased overhead.
Starting out, you may want to go with a lower rate to entice new business; you can always raise it later once you have established a reputation locally.
Remember, there is gonna be a ton of learning curve ahead; you will going from a few select (probably familiar) amps to being at the mercy of whatever comes through the door. You will get amps in that have no available schematic (many vintage amps meet this criteria) with bizarre issues and you will have to navigate essentially blind...and you can't charge the customer for your education. Be prepared to eat a lot of your time initially until you get your chops.
If you plan to turn away work you aren't comfortable with or choose to "specialize" in a particular brand, expect a tough time establishing a good reputation; though I admit it seems a lot of folks tend to buy in to the techs that claim to "specialize" in a particular brand. I personally don't buy it...if someone can supposably troubleshoot a Fender, they should be able to do the same with an old Hiwatt, Estey or Tiesco Del Ray.
Best of luck!