If you're pretty good at math, I'd pick economics over business. Business seems to teach you some theory behind the markets, but also management, accounting (boring as shit to me), when a company should make decisions, maybe some advertising, etc.
Econ will be about how the markets move and what makes them move, different trade and economic systems, etc. Seems to me the guys who really know whats going on have some econ background, while guys who run individual business are more apt to have the BSBA.
I used to want to be a broker. I went and talked to a local Edward Jones broker and he told me it doesn't matter what degree you get, you'll go to St Louis and they'll train you, you just need a 4 year degree. He also said you'll starve the first year, but if you make it one year chances are you'll be able to make a living off it. Of course this was before Ameri-trade and stuff.
Also, a futures trader buys and sells contracts for (usually) agricultural products on futures. But you can also trade on the future price of oil, where the markets will be, etc.
VERY risky, but of course you can make a lot of money on it too. Too risky for most, and I think hard to understand (too hard for me). Hilliary Clinton made a nice chunk on cattle futures back in the early 80s. She took like 12,000 and made over 100,000 in 10 months.
Basically, you buy a contract for something way in advance. Lets say back in the spring you buy a contract for November feeder
[email protected] cents per pound. Now depending on a ton of factors, including weather and the price of corn and feed, the market for cattle might be 91 cents per pound in November. If it is, then you made money, if its lower than 89.00 cents/lb, then you lost money (you agreed to buy at a certain price, so they make you buy them at that price). But very few contracts are carried untill the end, most traders sell the contracts in advance. Once you buy a contract, you can sell it prior to maturity, to either make some money or to cut your losses so you dont take a huge hit. Anyway that might not even be all correct....