If you leased bandwidth from an upstream supplier, what kit (specifics welcome) would you need to be an ISP provider for a few hundred people?

Just curious really, we're all sick of the customer service we get and I'd like to know what would actually be required. I assume you'd need a router/switches/server. Could you do anything with a clever implementation of IPtables? Would it be within reach of someone who's starting from scratch but happy to learn and is comfortable in a linux environment?