Spanners has summed it up. Can be very long hours, 12 hr nightshifts, work miracles with little or no support at 3 in the morning etc etc and normally with very little appreciation from those in the office doing the mon-fri 9-5 jobs. You will need your B1/B2 ticket to start earning some reasonable money but bear in mind the local BMW mechanic down the road will have a higher hourly rate!!!! Anyway, good luck with whatever you do, its not all bad...