For compensation maybe offer a choice of a one time payment or a 5-10% commission for as long as he works with you and the account is being serviced. Comission is safer, one time payment may be cheaper. If I had a trustworthy employee I would choose comission because it is more attractive and since it is 'for life' may encourage him to get more accounts to increase his pay (and yours). Though I would prefer it to be me the one getting new accounts.
This is just my opinion coming from a solo point of view. In a larger scale business this wouldn't be much of a problem, but in small scale business I would be wary of having an employee be a significant source of potential accounts in a specific area if they know him personally. Should he get in a fight with you/you fire him you may have to kiss goodbye to those accounts.