Always remember fish breeding is not a get rich quick scheme, Gawd knows I've been doing it for years.
Selling eggs would possibly be a better option as you personally dont have to worry about the skewed sex ratios or the feeding to get your charges to a saleable size.
Expect to sell 18 to 20 eggs for around a fiver and you will have to factor in your postal charges. possibly £1.50 if done correctly in the summer months(padded bag and insulation) and more if you include a heat pack during inclement weather.
Always include instructions on the species in question, when the eggs were collected and when they are expected to hatch.
Wait until the eggs show sign of development before sending, that way you earn a reputation of selling viable eggs.
Good Luck
ATB
C