Need help finding a bookeeper or someone to track and maintain all the billing

In the near future I will be acquiring 300 lots and want to hire someone to go over the billing in detail with the managers to make sure everythign is 100% correct on a monthly basis (late fees, water, monthly rent, fines, etc) . Those owners with several hundred lots, what system do you use? How much should I pay them and how do I find someone professional who I can entrust with this responsibility? This is something I definitely want to outsource. Each park has their own individual manager (3 parks total) and current owner spends countless hours going through each tenant individually.

Thanks…