I am looking for a field to study that will able me to earn extra money but no as a full time job (something about 20 hours a week)

Ive searched for web developers freealancers, they all seem to have many years of expirence.
I am not sure web developing is for me, so I dont want to put years of study before earning money.

my quastion is, for the average learner how long will it take to acquire skills and knowledge to start making money from doing something in this field of web developing? (I am not seeking for big cash)

would appreciate your advice