It's bad timing if you want to start shooting Polaroid... since Polaroid announced they have stopped making film.
At this point, I wouldn't waste money on an SX-70 unless you are rich and able to afford 600 film for over $15/pack.
Time-Zero is gone... even if you're rich, you won't be able to stock up on much Time-Zero, as it's going for $60/pack, and it's very likely it won't even work.
But the joy of instant photography is not completely dead yet. There are the Fuji packfilms that are still being produced. Many people don't realize that they are "Polaroids" because they don't have the classic white frame around them, but they are just like Polaroid's series of 690, 664 and 667... only a little better.
So to get started shooting "Polaroid", you need to get a camera...
The most useful guide available is the lovely Land List:
[That links directly to the packfilm cameras]
I've got a few of them for myself, and I've given a few of them