Yep, you can - the most important thing is that he's not profiting from the flight. You can and should be paid for the service of piloting as well.
Only word of caution I can offer is that flying for an owner requires really knowing your stuff as you may and probably will have to say no from time to time, due to weather/aircraft tech issues etc It may well happen that his business is delayed because you can't get where you're going. Be well briefed.
There's plenty of complexities but you should enjoy yourself as well.