How to use WCF for Business Logic layer(3 Sections - Account, HR and sales)

Question

Hi,
Can anyone help in Designing the artitechture with real Experience for the following scenario.
I have the following . . 1)UI Layer ,2)Service Host Layer, 3)Service Layer, 4)Business Layer, 5)DataAcess Layer.
In Business Layer have 1000 clases used for Accounts, HR and sales Activity. Some clases are common for all these 3 also.
what should be the aproch here? Should I go for 1000 services for each class?
Thanks in Advance.
Sunjib