@BaylightContracting  I don't have much to add to this, but the reason you can't assign Accounts Payable to the customer is because they're a customer.

Accounts Receivable is an account used to track what other people owe you; it is typically associated with customers.

Accounts Payable is an account used to track what you owe other people; it is typically associated with vendors.

Hence, you would not normally, if ever, use Accounts Payable to track what your customers owe you.