How much do I pay a coroporate promoter?

We're raising funds with the intention to go public. We've got a guy with 30yrs experience in the public sector, taking companies public.

What is a common way this individual would be compensated? i.e. would he get a percentage of the raise with an option for some or all of that raise to be converted to equity post-money? Or what is standard?

He is asking for an amount of shares pre-money that is equivalent to 7.5% total equity in the company.

No experience here, please help!