Oh, they've changed the buddy system since the last time I used it. It used to be a case of you needed a friends e-mail and you'd then input that to get an invite sent. Seems there are now open invitation links. That makes this much easier to deal with.
Though, on the down side, the inviter no longer gets a reward if the invitee uses a PLEX to upgrade their account. I used to simply give someone who'd used my buddy link one of my PLEX, they'd use it to upgrade the account, which would trigger my reward, which resulted in me getting a PLEX. It was a good way to give someone a 51 day trial without restrictions, basically. It's a shame they've clamped down on that... though I can appreciate why they did. Still, a shame
As for getting to the point you can support your account in 21 days... as others have mentioned, it IS possible. But the price is treating the game like a second job for those 21 days, and systematically sucking all the fun out of the experience. It's more than possible to fully support your gaming using in game money, I've been doing that for about 3 years now, but it takes a little to get to that point. I have always told new players that a good rule of thumb is to simply expect and accept that for the first 3 to 4 months you'll be paying for the game with RL funds. In that time, play it to have fun, gradually upgrade your ship, your skills, and meet people and simply enjoy the game. Treat it like a GAME. Because, that's what it is! At the end of that time you'll be in a position where, through a variety of means, you'll likely be able to earn the money you need each month to cover your subscription.
The only down side to that, is if your goal is to get to the point where you can cover your sub, as soon as you can, then you'll likely spend most of the time up to and for a while following the point you can do that, very poor >.< You wont be able to justify replacing ships easily, you wont be able to take advantage of cheap ship deals if they're not directly going to benefit you (that curse sure would be nice for PvP, but it doesn't help you run Level 4 missions so it's no good for now...)
As with RL, ultimately, it takes money to make money. So the first focus is to get enough money behind you to support whatever your endeavour is going to be (mining, missioning, ratting) and then just let your money amass while you do that and have fun. Once your funds are at a few hundred million, then start thinking about what to do with the money that could help you get more, and just let it build up from that