Avira, Avast, Microsoft Secruity Essentials and AVG ( ok so they bricked some computers a few months ago
) are all free and just about as good as anything you would pay for. I have used Avira / Malwarebytes / CCleaner combo for well over a year with no problems ever. I have put Avira on every computer I have built since ( 20 to 30 ) and have had not one infected with anything.
I did used to pay for Kaspersky before I read a PC Magazine article doing some in depth testing showing the free solutions just as good as the paid ones.