I agree with xStep here. All the wedding videographers are advertising HD nowadays. You'd be at a distinct disadvantage if you only shot SD. More and more folks have HDTVs now and want/need/expect HD wedding videos.
As for the camera ... I don't think a HF100 will cut the mustard either. Sure, it's HD, but it's a consumer camcorder. I don't know all of the specs, but does it have a mic-in port? How about a hot-shoe. I'm also not sure about using SD cards. I'm sure there are other features that you'll need to make pro-quality wedding vids.
If this is for a business, then you might want to look into a pro-line HDV camcorder. I'm no pro, but I do know that in the wedding industry, image counts for a lot. The bride will likely interview with several videographers. She'll see guys with the huge pro cams and compare that to the tiny HF100 and think "gee, size matters, right?".
And since it's a business, you can write it off as a business expense. Equipment gets depreciated over 7 years, right?