Woah there sweetie...sounds like you're more than a bit confused. Wanting to be safe is an excellent idea. However, buying birth control pills from someone else is a terrible idea.
First of all, you cannot start taking birth control pills without seeing a doctor for a full gyn exam. Birth control pills are not absolutely harmless, for some women they can be dangerous, and that's something only your doctor is going to be able to tell you. Secondly, the pill is not something you can just take when you want to have sex and it'll automatically protect you. Pills come in packs with the days of the week labeled for a reason...you have to take them correctly. That means that everyday you'll be taking a pill at the same time of the day. You have to be on them for at least one full cycle before they are effective. So you're not going to be able to buy pills from your friend. You would be putting yourself at risk potentially, and they would be completely ineffective, and your friend's cycle would be all messed up because she'd be missing pills. So once again, buying these pills is not an option.
By the way, there is no age requirement for obtaining birth control pills without parental permission. Why don't you try contacting your local Planned Parenthood office for an appointment and a discussion of your contraceptive options (make sure you ask them to explain exactly how the pill works so that you understand what you have to do to protect yourself). You and your partner should also get full STD screens while you're at it. Using condoms is a fabulous way to protect yourself from disease, but you need to be screened anyway. Never having had sex before does not mean you're free from disease...STDs can be transmitted in nonsexual ways.
The best advice I can give you sweetie is to read the articles on our site and to call your local Planned Parenthood office. Its good that you're concerned about protecting yourself, but you need to get a better understanding to how to do so, and how your body works. There's no rush to have sex, get the information you need first.
Scarleteen Advocate (and Labia Lady)
"The whole world is full of morons...they just congregate on the internet cause it's easy for them to push the buttons."