Slicing pie specifically deals with this as Hai mentioned. Every startup thinks they are worth millions when they are only an idea, and every new contributor thinks they're worth a mint just for turning up. By having a candid discussion about fair market value (not hoped-for, "if it all went well" type values) for each contributor's time, and slicing based on income forgone, you get a fair reflection of the changing value of each contributor's share. As a sales guy, the potential is that your fair market value is higher than for a senior developer, and that's a tough discussion, but the 'normal' market has already worked out the relative values for this.
Caution though: "I have this amazing network and can sell" is a promise, not a reality. A good sales person puts a fair share of their income at risk via commissions, and you might need to double dip. That is: risk your 'income' in the cals, plus have any income paid in equity. A double dare, perhaps. Your share of the slicing pie would be based on a notional base pay plus commissions you earn from sales actually delivered.
If, after 12 months you have delivered nothing, then your share should be less than your tech counterparts (assuming a normal base for you would be less than their salary), and you should be sacked for non-performance - leaving with a small share that declines as they continue to contribute.
If, after 12 months you have crushed it, then you might end up as majority shareholder. Both of these extremes are fair, or at least as fair as can be achieved. The tech with the "idea to kill all ideas" and the sales guy with the "roladex to die for" get nothing for vacuous puffery, but get fairly paid in a new economy way for their contribution based on old-economy values.