Ya keep your money. If you really need to check if he gets sea sick take a charter out and that will give you a better idea. Safer and will give ya an idea what you are in for.
__________________ Member <<<--Ok I will take a shot at it..
Like they said, your buddy shouldn't get too seasick in the harbor since there are no swells. But if you're thinking about ending up with a fairly small boat, going out on a larger charter vessel might not give him the full experience. Some of my friends do fine on a larger boat, but get pretty queasy on my 21'. I agree on passing on an inflatable like that one.
You can go to the harbors and rent a kayak for around 10-20 an hour to get the feel..then look on craigslist for a yak...I just got mine at a yard sale for 200 bucks and it does the job.