I think your plan sounds reasonable, but it's tough to breed and sell enough hatchlings to support your collection. It takes a lot of time and upfront expense, especially if you raise your breeders from hatchlings like I do.
Aside from rodent costs (which increase sharply once your eggs hatch) you'll also need to buy/build an incubator, and have enough available enclosures for the hatchlings, which means buying more thermostats. Vet costs are always a possibility too. Breeding females may become egg-bound, prolapse, etc.
Luck is definitely a huge factor as well. For instance, last year I had a Ivory x Yellowbelly clutch where the offspring had a 50/50 chance of being either Ivory or Yellowbelly. Ivories of course are priced considerably higher than Yellowbellies. 5 of 6 hatchlings were Ivory. But they could have just as easily all been Yellowbelly instead, the odds being equal.
I'm not trying to dissuade you. I'm just trying to give you a realistic perspective. I've been breeding as a hobby for 4 years now. It's a slow process, and I've put a lot more money into it than I expected when I started out. But I enjoy it, and have no regrets! If you're interested in breeding, then by all means start some projects of your own. Just be aware of the costs and risks, be patient, and don't get in over your head!
Anyway, BELs are easy enough to produce. When you're looking for your double hets (double het for what besides pied?), see if you can find combos that include butter/lesser/mojave so you could make BELs along with your recessives.
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