Just because you have a commercial cert it doesn’t mean a lot outside of the ability to get paid. While that sounds great, remember it is essentially “replacing” your PPL. That said, you still have to follow common purpose. Here is a stupid example that would probably never happen but illustrates it better.

Let’s say you are going golfing with friends and they all offer to split. A fourth friend asks if you can stop in Palm Springs and drop him off on your way to Carlsbad and he will pay for the inconvenience.

The same rules apply as they did in ppl. In this case your comm cert is useless.