Hello there wellcome to P8ntballer.
Your age shouldn't be a problem, if you are looking at the CPPS have a look at this section
http://p8ntballer-forums.com/forums/cpps.34/
It may be worth pm'ing Rich HARRIS for more info.
Their facebook page CPPS
http://www.facebook.com/group.php?gid=44407531513
Web site
http://www.ballsoutpromotions.com/_pages/aboutus.html
Where abouts are you based there may be a local team near by that are looking for new players.
Just to let you know that you have posted in the wrong section Talk to the mods is for any problems you have.
If you have newbie questions it is worth having a search in this section or posting up
http://p8ntballer-forums.com/forums/newbies.27/
As for what type of marker you are opening up a big can of worms. We all have our favorites, I like ego's, others like Geo's, mini's axe's, Dye DM's/NT's, Smart parts ion's, etc etc the list can go on and on.
How much have you got to spend? What is your budget, also you need to take into account of the gun, hopper, tank, mask as the basics then you have clothing, spares etc etc.
You will find a gun in the for sales thread, Have a look around get an idea whats on offer..... If you miss out on one gun another will turn up.
Regards and enjoy P8ntballer
Ants