You should definately be prepared to keep your snake's offspring should they not sell right away. Equip yourself with the proper baby racks, tubs, heating and thermostat before you even think of breeding. A top-notch incubator is also needed; researching that is a must. I tried going the easy route and had a cheap Hovabator fail on me and it cost me 2 cluches.
That being said, it is not always easy to sell your snakes, especially if you do not have a reputation to go back on.. factoring in the cost of the incubator, the money spent on feeding your snakes, tubs for future babies; I do not think that you should count on making back the money you spent on the original snakes. I still have to do my own math personally, but I do not think that I did!