Depending on your position, you will be earning between $40k and $100k. Chances are that you will be working for some sort of government agency, and that means really good benefits. You will have top-notch healthcare plans, possible pension/401(k) plans, and ample paid time off. The more time you put in, the more you will make. So be patient and keep learning.
The best investigators will rise to positions of greater responsibility and more money. If you rock at your job and have ambitions to live large, then you can become the director of the FBI. If that's the case, you’ll be raking in upwards of $200k and eating lunch with the President.