If you decide to buy antivirus software instead of using those you can download for free, then you need to buy antivirus software from a reputable antivirus company. Don’t ever think that since you will buy antivirus software and not just download a free antivirus program, then you are safe. There are antivirus companies who are only too eager to lock you in their antivirus software lineup. Don’t buy antivirus software from them.
Research a company if you plan to buy antivirus software from them. If you are not familiar with antivirus software, determining which antivirus company is trustworthy could be hard. I found a list by Microsoft of antivirus software companies. Wikipedia also has its list of antivirus software. Wikipedia’s list is nice because antivirus programs are compared to each other by operating system availability and boot-time, among others. It also includes a list of antivirus programs free to download. Don’t buy antivirus software without checking these lists or that of reputable sites like CNet or PCMag. Your internet security depends on it.