Money wise I was lucky....
I didnt really get into p8ntball till I was 16/17, by then i skipped my paper round jobs and sunday market cleanups and was doing a Ford Apprenticeship and started marshalling at Mayhem for Rob. Combined I was taking home roughly £190 a week!
What Im getting at is some apprenticeships are really good, and if your into the getting paid for a skill and qualification course then go for them. If you get the right one they even give you a job at the end of it, and every year the amount you get paid goes up
Also, not being funny I still wouldnt have paid the guy 100quid cos theres nothing to say he will send you the gun. He could take your money and run with the gun also. A meet up at a site would have been better, least that way you can see if it works and you get to walk away with the gun if you decide to pay!