Why would you vest an offer worth 3x revenue over 4 years unless your business was about to collapse? That's an atrocious offer as stated. You should get 3x earnings today (or some multiple depending on prospects and margins) and earn out more over 3-4 years.

Edit: Sorry I must be tired. This is a revenue multiple not income. Revenue multiples are not particularly helpful in valuing a company with a mature business model. Gross profit would be far more useful.