B2B setup

I need to find out if Zen Cart can perform the following.

1. Allow discounts to some users and not others. Basically, I setup an account for a customer and assign a discount to them.
2. Instead of checking out to a payment system, just create an invoice for manual payment.

My requirement for the site is to allow business customers to order products at a wholesale price and receive and invoice rather than paying up front. I will only have a few products for this site as it is a niche site for a specific set of goods.

You can create discount groups and assign customers to them. There is no limit that I know of on the number of discount groups.

You can use the "check/moneyorder" payment module, and change its wording to suit your needs. This will allow checkout without immediate payment. The customer receives an itemized e-mail invoice. You can set order status as desired manually, when payment is actually received.