Personally, I would buy from a breeder. and not support pet stores. Try to bargain for price since you are interested in buying 4 units. I would think 1.3 - 1 male and 2 females. If they are 4 inches, you have 2 or more years to wait until sexual maturity...also feed them daily, to grow into strong and capable young adults.
Hey, Im also going to soon get into breeding star tortoises, however I'm going to buy an adult pair. I am also located in florida, and heres what I know. Stars CANNOT be kept outside in sw florida. We have humidity in an upwards of 70% here, and about 40% is just right for stars. For a short time, (for example, summer monsoons) its fine, but they can't live full-time in it, as it will cause respiratory issues and probably eventual death...With animals this expensive, fragile, (and with their wild numbers we need to keep as many alive and breeding as we can) I would definitely build them an indoor enclosure. Try star tortoise.net, they have basically all the information you could want about anything to do with stars.