Like with any government job, there are very strict pay scales that are used to determine how much you would make as an FBI Special Agent. Well, they don't literally use scales; they're not Ebenezer Scrooge. The General Schedule (GS) that the government uses consists of 15 "grades," and each grade is made up of 10 "steps." As you work your way up the pay scale, you'll make more money obviously, but FBI Special Agents are also entitled to extra pay benefits.
FBI Special Agent trainees at the Academy in Quantico, VA, and new Special Agents start out pretty high: GS-10, step 1, which is about $45,000. Not bad, right? That's not all, though; Special Agents and trainees also receive a locality adjustment ranging from 12.5-28.7% based on their assignment. (Trainees receive a set locality adjustment of 17.5% because they will be assigned to Quantico, VA, for the duration of their time in the FBI Academy.) With this locality adjustment added in, trainees are set to earn around $50,000 a year. Even not badder.
New Special Agents also have the added benefit of receiving availability pay, which is a 25% increase in their adjusted salary (base pay + locality adjustment) since they are required to work an average of 50 hours per week instead of the standard government 40. After adding in all of these adjustments, new Special Agents are set to make between $61,100 and $69,900 their first year based on where they are assigned. And no, that doesn't mean Agents are paid more if they are assigned somewhere that isn't as "cool." Location adjustments are made based on cost of living in an area, not how bumpin’ the nightlife is.
And remember, that's just the first year. As we said, their earnings are based on a General Schedule that allows for periodic pay increases in line with other government employees. GS 10, step 1, is only a base of about $45,000, but GS 15, step 10, is closer to $130,000. Not every FBI Special Agent is going to end up making that much, but the potential is there. And once you enter in bribes, hush money, and stolen drug caches, you're pretty much set for life.