Hi 320_Wannabee,
Few answers to your question...
1/ It depends on how long it takes you to get a job with an airline that flies 320's!! Sounds obvious -let me explain further!
Some people take a 14 month full time course to do their professional exams and then maybe go straight into an airline onto the A320, so the minimum time from 0hrs to A320 FO might be (including 1 months 320 training) 14-15 months! Others spend years part time training and working on other types/ with other companies before flying the 'bus -Some may never fly it in their career- through lifestyle choice or working for a non airbus operator.
Depending on the airline and circumstances in the industry it can take anything from 2 months (with enough previous experience on other types) to 15 years to get a command (become a captain).
2/ Pay -again depends on the airline but in the UK a jet FO in a company with 320's on average earns 35000+.
3/ How to get the job? Well try a search here on pprune the answers will be varied and often poles apart. The trick is find a route that suits you. At 15 I was working towards my GCSE's reading everything possible about flying, in the RAF cadets. Then did sciencey A-Levels. At 17 did my Private pilots licence, went to Uni (engineering) and then sponsored at 21 to fly and have been on the 'bus for about 2 years (and love it!).
There are a million and one ways to achieve your dreams but the vast majority of people in the industry have one thing in common -a love of flying and an absolute refusal to accept the setbacks that WILL occur on the road to the flightdeck!
Incidentally, much as I love flying the A320, I'd be equally happy flying anything and still fly for fun in light aircraft, and my mates on other types enjoy their jobs just as much too -so don't get too fixed on the A320!
I wish you all the very best in achieving your ambitions,
Best regards,
CTB