How old are you?
Is they anti - guns or just won't let you have a paintball gun in the house?
Could it realy be them avoiding you buying tonnes of gear for a 'phase' you are going through?
How much paintball have you played / what type?
Any family members/family friends paintballing?
Can you get away with starting to buy the other essentials such as mask etc and playing with rentals?
Have you looked into the 'cost models' of paintball? - Punters, walkons, big games, tournaments etc
Consider some of the above and produce 'evidence' to support your need for your own marker.