when I needed help with my first frame-up build, my mech told me to bring in all the parts after he had closed up shop for the day.
I brought the frame, parts, good beer, and a pizza...
once we were finished, I took the bike out in the parking lot, ran thru the gears, tried the brakes. everything was perfect.
he absolutely refused to take any money for his time. said he had fun working on something 'nice' and that wasn't covered in dirt and grease.
I dropped off another six pack of beer the next day, he was pleased with the 'tip'...