[ohsnap]

How were you contacted? Is this through a personal connection or is he fishing?

I'd suggest to ask for references. Follow through references and ask about how he/she helped them. I'd also make it clear up front that you have little capital to pay him or any marketing strategy - he might be assuming you have the money to do so.

Equity is typically not milestone based. You would typically agree to a form of 'sweat equity' - meaning the amount of work he puts in for a piece of the company.