You must be hired as a special agent first, and expect to work investigations for up to two years before taking on collateral duty (aviation division). They fly a lot of GA assets, as well as Lears, helo's, and Citations (unless you're former military with goggle time, helo's are a LONG shot). The work is mostly aerial surviellance.
Pay starts anywhere from GS-5 to GS-9 depending on qualifications. Most S/A (special agent) applicants have graduate work, previous law enforcement/militaty experience, foreign language skills, and spotless records.
You're a criminal investigator first - flying comes in second, and is very mission oriented.
J.