Okay, so I'll answer these:
1) It all depends on what morph and type of snake you're looking for. Certain breeders focus on certain morphs while others focus on something different. Also they may focus on certain species, so you have to figure out exactly what you're looking for. Another factor coming into play is the quality of the morph you're after if you decide another BP.
2) I would switch to a rack system becaus aquariums take up space and you don't want to keep the BPs all in the same tub or aquarium. Racks hold humidity better and are more space friendly.
3.) Yes they do, you can get racks that only have 3 slots and since you're in Florida you can get it cheaper versus having to pay the shipping. I can refer you to a person who does racks and is very popular. I have a few of his racks myself.
4.) You can, but it's generally not recommended because different species thrive in different temperatures and humidity levels along with other reasons.