I am sorry Micheal for my less thsn serious answer to your perfectly good question. I see the moderator has removed it and quite rightly so. I was just having a laugh!
Seriously, like the reply above, a freight pilot has to have the same qualifications as any airline pilot. An ATPL in the UK.
If you are serious about a career in aviation, it is perhaps a good thing to make a bold decision when you are young. Most airlines like to get as many years out of their pilots in return for their investment.
Ways of doing it can vary but the best way to start is to get involved in some aviation activity.I see from your previous post the you are about to get your PPL. Thats a good start and well done for doing it at 17!
I am a Flight Engineer and wish I had made a decision when I was your age to be an airline pilot!
If you are ever in the Manchester area and want to go flying,send me a PM and I would be more than happy to do a few hours in the old Cessna.
Hope this answers some of your questions!
Coop & Bear