If you will configure Comodo Firewall properly, you do need an AV! (Please understand this first)
So you do not need to pay to ESET just for an Antivirus.
If you are using Wİndows 8 or higher, no need to 3rd party antivirus. Windows Defender already set and gives your a real-time protection, without false positives.
If you are using Windows 7, Microsoft Security Essentials or Avast Free Antivirus will be a good choice for AV.
These antiviruses detects many and if something escape, we have CFW
Keep your money in your pocket and buy yourself a beer!