As career trader, the salary you get is just enough to pay your bills. For example ~100K in NYC. If you and/or the desk you work with make(s) money, you get a bonus somewhere between 8-12% of the profit you generated. Bonuses are paid annually around Jan/Feb. So, you need to wait to see your piece of the pie (if any).
If you break even the first year, they may give you a lifeline for another year. If you lose as mention above, you likely to get booted out.
There are other issues such as risk management limitations, they come after you or liquidate your positions if you have high overnight exposure. So you have volks breathing down your neck on a daily basis. You cannot take wild bets with bank money and must work by the rules. In addition, each trader has a annual "budget" which is the target trading profit expected from you. If you meet or exceed your budget you'll be celebrated (at least for a couple of months).
There are some perks as immediate IT support, quantitative finance support, etc.