The cheapest prof is cooking and costs less than 1.7g... That's making 2 giant omnomberry cakes to make a profit...
For JC if you don't resell everything you make (and don't need) you'll spend 5-8g, for the heck of it I'll go with 10g, jewelery gives about 20s profit so to be break even you need to sell 50 (peanuts)
I can do this for all profs if you insist.