The third highest ranking (Farmers and Merchants)
What Life Would be Like
First off, you are born into your ranking and cannot move up or down. So, you get what you get and basically just live your life! Once you are born you are to learn different skills to succeed later in your life. Some of these are to know the correct trading prices and offers, and another is trying to learn and understand good management. You are not treated horribly, or bad for that matter. You would practically just be neutral, nothing special, but nothing horrible.
Back to the topic of their future work, they would normally be a merchant or a farmer. To be a merchant, you would need to learn time and money management to become successful. As well as knowing correct trade terms and pricing. To ensure you would not take the wrong choice. For a farmer, there is not to much to learn except agriculture. How to plant crops and other items was necessary.