Yeah, but profit sharing is based on a percentage of your qualified wages. So if you start in December you will be eligible for profit sharing but, you will only get 10-14 percent of what you worked for the entire year, ie. December. So, your profit sharing will equal a couple hundred dollars. Not that big of deal in the grand scheme of things.
However, I echo what everyone has said and take the earliest class you can, just don't let the lack of profit sharing for one month be one of your main considerations.