Pete,

this is exactly what happened to me, bought a key coding machine, enquired about obtaining security codes and where to buy keys from and thought good up and running.

Problems soon cropped up like not being able to communicate with ecu's, wrong chips in keys even from dealers, customer supplied own keys and so on but the ones that were successful were all good easy money earners.

I tried to charge around £40 but sometimes felt very embarrassed when the customer is standing next to you and coding in a key takes 5 mins (mainly on Vauxhall's) and then you asked for £40 so quite often charged £25 + key if i supplied but being mobile i'd expect to pay £40+.

Another suggestion if you haven't is to phone dealers up as you'll be very surprised how some charge less that you think.