I can tell you now that 3 snakes is not worth it, even with the future babies. The only way it will be worth it is if you overproduce and sell the extras.

I really like this website for info on breeding and such: http://www.metalmonkeyexotics.com/blog/?page_id=163
You might want to look into raising African Soft-Furred rats if all you're going to have is BPs, but be aware that if sometimes the babies can be harder to sell if they refuse to eat regular rats.

I've been raising rats and mice since November, but have not completely paid off the initial costs plus the ongoing ones, even though I produce way more than I need and sell the extras. I have about 9 breeder girls that generally get a week break after a litter before going back to breed, which is healthier for them than back to back litters. I probably sell 90% of what I produce, so you can see, with the 6 snakes that I have (7th is a new rescue), if I didn't over-produce, it would actually cost me more money to breed my own, even if it was scaled down in size.