The stock market dividend yield is a decent analogy, but with ball pythons you have to remember you are constantly paying into them. If you buy your food directly you pay for it and that cost has to go into the snake. Also if you breed your own feeders the cost of breeding them has to be added in plus the time spent. The you throw in the energy needed for keeping them as well. Plus you have to throw in the second "stock" you had to buy. (The male as it takes 2 to tango.) Also you have the cost of the incubator and housing structures which can be spread out over several females or several years of breeding.
In the end if you are hobby breeding the best you can hope for is selling to help supply your addiction. If you are looking at making it a business you have to create and balance a business plan. You are probably looking at 3 years as a minimum to make the business self sufficient and 5 years minimum before you actually see a profit. A lot of this also depends on up front investment. If you invest 5 grand in start up it will take longer to recover than if you invest 20 grand as the cost of incidentals will be spread out over more ball pythons. Also though you are exposing yourself to more risk though.
Also I don't imagine it would be easy to get a loan for this kind of business until you have actually hit the point that your balance sheet is showing a profit for a couple years in a row at which point I'm not sure if a loan is really something you would want to mess with as the interest will cut into your profit pretty hard!