^^ Correct.
Cat 5 is where you--and everyone else--will start. 10 mass start races gets you to Cat 4. From there is points based on races, your place at the finish, and the group you compete against.

You can use day license for $10 to try racing. Just show up to the race, fill out a few forms, and pay an extra $10 to race with the Cat 5 group. This is sometimes called the 'Citizen' race, since nearly anybody ca show up and race.