Pros:
Fertilizes eggs, reducing dependence on hatcheries to replenish stock
Protects hens (my hens have been saved by my rooster multiple times)
Keeps hens from fighting too much
Helps hens find food
Yard Candy!
Cons:
Some level of aggression may develop, and it's quite likely
Too many roosters/ not enough hens can lead to stressed hens. I prefer at least six hens to a rooster, any less and I start to see problems.
Crowing from 5 AM to late in the evening every single day
As far as being "a waste of space and feed," this is true if you have a lot of roosters, but one more bird doesn't take up a whole lot of food. They're probably the cheapest "pet" as far as feed costs per animal.
Since you still live with your parents, I think you should take responsibility for the chickens if you want to keep him. Help with costs, wake up early every morning, collect eggs, feed, water, clean the coop when it needs it, etc.
A hen can take the role of flock guardian, but that doesn't mean they'll be good at it. Mine sucked at it when I had just hens. A rooster is very strong and can leave quite the mark, which can be both a good and a bad thing. Good when he uses it on a stray dog, bad if he uses it on you! If you don't free range, however, I don't think you really need a rooster for protection either.