I guess you need to determine whether you are using your PC as a business tool or a home computer. If you are working and charging customers (even if you don't yet make a profit), then it's not home use, so you would need the purchased version. Of course your accountant would offset this cost as a business expense.
The commercial version of AVG offers far more than the free version and at such a low cost, I'm surprised that more people don't buy it
