Some of the recurring issues in a startup is how to split equity and ownership. It is an important topic and is better to be prepared to deal with it from the very beginning.
Here some good advice:
- Forming a new software startup, how do I allocate ownership fairly? by Joel Spolsky
- The Equity Equation by Paul Graham
- How to start a startup by Paul Graham
And the capitalization table from Fred Wilson is an essential tool to show how much everyone owns of the company: