Until you know what your potential clients want, have them buy the string and pay for labor. Buy string that you know you will use, unless you get a great price. I've had a couple of reels that that took a year to use up. No use in tying up cash in string stock, until you get regular clients.
Machines: Gamma 6004 2-point w/ Wise 2086 & Babolat Sensor Dual