Can we limit the amount of "Potentials" a user can have at one time?

Can we limit the amount of "Potentials" a user can have at one time?

I've been trying to find a way to have limitations set up for my sales people. 

Before approaching any business, our sales people conduct research on the prospect. Since the salesperson does his/her own research, we want them to be able to create the Potential on their own. The fields are already customized to fit our research needs, so that's not much a problem. 

The issue arises because we don't want all our reps to start claiming too many prospects as their own. We want it set up so that they can have a maximum of 10 prospects they are researching at a time. During this research, the "Stage" field will be set at "Research In Progress." So essentially, we want only 10 "Potentials" at a time that have the "Stage" field set to "Research in Progress." Once they approach the business, we would like for them to update the "Stage" field to "Contacted", which will then allow that user to create another Potential. 

If anyone can find a solution for us that would be great!! Thanks