For the long run, as a professional business, it's better to get setup with a reseller account, than purchase 1x off discount boxed software from various "who knows what" sources.
When you first get setup with a reseller account, yes at first your discounts will not be that large. But as you build volume, you start getting deeper and deeper discounts. You also have the ability to renew the same licenses, track expiration dates, purchase and track all the various different types of software (important as you move into supporting SMBs from home users)...as you can now employ that volume you've sold towards reseller the SMB/Enterprise versions of the antivirus product to your business clients.
1x stop tracking of all your sales, history.
Access to marketing materials and training materials, you get SWAG, promotional stuff to put up in your store, and mailouts/promotions.
Access to superior reseller support
Access to sales reps to help you in bids
In the long run, there are SOOOO many reasons to take this approach that help you come out ahead.