Some benefits of being a merchant in the middle ages, was that you were able to travel the lands, & were not forced to stay in a area. You were also relatively rich, & if successful, can have many things, including land, wealth, etc. Also, people bought from you (especially if people trusts you, you have good history, & you give fairly good prices). This gives you constant source of money, & people to back you up when you get in trouble (depends on what the trouble is tho)
hope this helps