It's tough to say where to start but here are a few thoughts late on a Friday afternoon:
1. I'm assuming you're talking about Java Development. Do you know Java? Check out This Link at RIM
for your options.
2. Simulator development isn't great, but it's not unusable either. If you're just starting out, it lets you get your feet wet without having to lay out any capital.
3. Once you know what you're getting into, get the Signing Keys from RIM ($99) and a device.
4. Getting a BES is something that depends on the investment you're putting in as well as what type of apps you're developing. Avoid it if you can