My best friend was in the bee business for years. He really loved it, other than it's become a very tough business to make a living in unless you're a huge outfit. Basically, they need to be placed where they can get food... pollen. The honey that they produce is their food. We just steal it from them for our benefit. The largest cash reason for bees is not honey, but pollination. Where we live, the "stuff" they make their honey out of does not make for good clear sale able honey, so he made his money on pollination. He'd make an average of $25/box for a season. The goal is to get boxes into multiple seasons and pollinating different crops throughout the year.
In winter, at least around here, he had to buy syrup to feed them with, which of course costs more money.
As for when the box gets full... they may swarm. They will go looking for another place to live, and either find or create a new queen. Sometimes the colony will split itself, but usually they will all leave and leave you with an empty box or "dead-out". To some extent, they will self-regulate the colony size, but it'd be tough to keep one box alive for long. Usually, they are split up, and a new box is created. That's the easiest way to grow your "business".
I think it'd be great for you to try, as there are not enough bees to go around right now. They are suffering from something they've termed "colony collapse" right now. Beekeepers all over the country are trying to figure it out. They have come up with every reason under the sun, from mites, to pesticide, to cell phone radiation. My buddy spent his winters in the almond groves in Kalifornia, and said that last winter was crazy. It'd be the middle of the night, and here would come guys in ties from universities all over the world wanting to interview him... in the middle of the orchard!!! What's happening is the queen will go sterile after a period of only about a few weeks. The colony will boot her and attempt to create a new one. Over time, the colony can't sustain itself. When my friend left the almonds in the spring of '06, he had nearly a thousand colonies. By the time he loaded up the truck in fall of '06, he had just over 400. That's a $15,000.00 loss before he even expenses anything out.
Bees also have predators. Around here, the biggest one is skunks. They will scratch the front of the box and just sit and lap up the bees as they exit the hive. A family of skunks can wipe out a bee yard in just a few evenings. That makes it necessary to be in the field at least a few times a week checking your yards.
Most beekeepers are really nice, so yeah... find one and BEEfriend him. It will be important when it comes to things like medicating, feeding, extracting honey, etc. You sure don't want to buy all that equipment for just a hive or two. Then, go start knocking on doors of farmers, ranchers, and the like and find a place to put 'em. <img src="/forums/images/graemlins/kewl.gif" alt="" />