As a property investor, mentor and developer, I have worked with numerous brokers and agents. To become successful in the real estate sector, you actually need three things:

1.Positive attitude
2.Lots of energy and
3.Techniques on how to close the sale.

With your background, to choose which one is the right course for you, you need to ask yourself:

.How much money and time can I afford?.

If I were in your shoes, I would do it this way:
1.Do the Century 21 course( because least cost, time and gives you the license)
2.Sell a few houses, set yourself targets and work your way up. Work with a successful agent as an apprentice.
3.When you think you are ready to go to the next level, do the community college course, or by this time lots of other doors will open to you.

Finally, remember, it is a journey, not a destination. Wish you luck!