My son, who is a mature 3rd level student, doesn't have a fixed income. However, from time to time, he works part-time. He is thinking of buying shares occasionally, from time to time, when he has a bit of surplus cash, to build up a portfolio gradually. What is the minimum amount he can buy? For example, he is thinking of buying Ryanair. If he opens an account with, e.g. Goodbody, what would his expenses be?