Other than collecting MTV's checks, of course
MTV has made a mint off of their shows 16 & Pregnant, Teen Mom OG, and Teen Mom 2, and they reward the moms of the show accordingly. Though some of the girls choose to have regular jobs or have gotten an education, they make enough money filming the show a few months out of the year to not need other income.
The men featured on the shows also receive some big checks for their cooperation, but they probably aren’t pulling down what the ladies are, so they need to have some extra cash to get by.
People on reality television have to do something with their time, other than complaining about what’s going on with the people in their lives.