1) commissions, orchestrations, competitions, busking on the street, teach composition, etc.
2) possible but rare, look at the great composers, Bach, Mozart, Beethoven, etc.
3)Networking. Thats it.
4)You do not NEED a music degree or portfolio, but It is highly suggested that you have both.
5)Have fun. Be Yourself. Make some music for yourself. Not all music you make you will like but may sell quickly. Website: The Portfolio Composer