Err, no. There’s the cofounders, the investors (may or may not be the same people, may change each round of investment), the future employee options, the vesting schedule…, the dilution agreements that happen at each investment round, what happens to vested and unvested stock at each investment round, cliff agreements, parachute agreements, and that’s just off the top of my head. 23% can mean so many different things based on the fine print.

This is why you hang out in venture capitalist hangouts. So you can get brown bag stories from venture capital attorneys, who you pay for a personal consult asap on any contract you are planning to sign and rely on to protect your interest in the sweat equity you are about to commit to.

With few exceptions, most wantrepreneurs overvalue their own vision.

The import links for your question:

Joel Spolsky’s guide to equity on startups

Khan Academy’s Business Life Cycle: from startup to bankruptcy

The Business Plan excerpt from Neal Stephenson’s Cryptonomicon