Quote Originally Posted by Jefals View Post
So, the next time somebody wants something a little different. Instead of the residential customers, they want residential customers with good credit. Now, do I make another class for this, where most of the code is the same, but just minor difference? Or they want commercial customers instead of residential.

Let's say I know that I'm going to have lots of requests like this, but they're all going to have slightly different "wrinkles". Would I still make a class for something that's probably only going to be used by one application? Or, make a more general class -- ( say, I know they always will want the customers whose numbers are greater than 10, and they will always want at least the name and address). Would I just put that general stuff inside the class, and then code the particulars outside of the class?
No, you don't need a separate class for each type of customer, unless they differ from each other in a very significant way. A customer is a customer and the type is just one of its properties.

A class can have properties/fields, behavior (subs/functions), events.

What you are saying is just a property of the customer. So
Customer Type (Residential/non-residential etc.)
Credit (good/bad etc.)

A class will always be required. It is a like a template for your objects. It helps in creation of your objects and defines its properties, behavior and events.
It is always a good idea to code your classes in a general way, though if you know that you will never never need any customer data with number less than 10, you can put the restriction inside the class.