As Donna mentioned in her comment, AVG Free is a great anti-virus product. However, the free version is for personal use only. Businesses are required to purchase a commercial version of the product, so it should not be considered freeware for business users.
Dan makes a great point in his "Leasing benefits" section about "total financing". A lot of people don't realize that you can lease software too. Businesses that require expensive software to get started, such as design firms and software developers, can use a lease to spread out the cost of that software over time. The ability to begin revenue-generating activities immediately will more than offset the additional long term cost of the lease.