Most merchants formed an association named the guild. It was created to encourage trade and control it. Most English towns had craft guilds. In London, there were specific guilds for each seperate craft. Members were heavily fined if they made shoddy goods or used false coins or faulty weights and measures. Masters as well as workers were in this association. An apprentice would not be paid but would live in the Master's  house for usually seven years. Then they became journey men working for each day. If they wanted to become a Master they had to prove their skills by making a "Masterpiece" and by paying large amounts of money. That is why many highly skilled craftsmen never became Masters: it was too expensive.