Sounds like a definitely workable plan! The sex ratio of hatchlings is a pretty consistent 50% so far, despite all efforts to manipulate it, so if you bought 3-4 babies you'd have a pretty good chance of ending up with both male and female. It takes many months for "cresticles" to become visible, but if you have an 8x or better jeweler's loupe, you can sex them by checking for preanal pores as early as 3-4 months. Then you can plan ahead for what you need or want to do as far as selling, keeping, separating, etc.