That does not sound realistic. OP,
First of all, it is not like television or the movies at all. It's not people who look like models, fight like Bruce Lee, shoot like Annie Oakley, or satisfy their partners like Don Juan. It is hardly romantic, and really just a mundane job like any other.
I am going to give you a somewhat different answer that you might expect. We know that the media, such as television and movies, has a large influence on peoples' perception of agencies like the FBI. The job of FBI agent however, is not at all like TV.
You should start with research. Research how the FBI acknowledges its own deception in using informants. Research the federal civil asset forfeiture program that has exploded. Research how that money is used to pay those informants.
Suspects are caught mostly because law enforcement talks with people. Take a look at the FBI. Their website reads that they use "elements of deception, "intrusion into the privacy of individuals," or they cooperate with people when they know their "reliability and motivation may be open to question."
Here's a Pittsburgh Post Gazette article on paying informants from Feb 2015. It states that payments to confidential informants has increased.
2014: The federal government gave 500 billion in reward money to snitches.
Confidential informants received millions. One informant got almost thirty million dollars from one government fund.
They are paid from the federal asset forfeiture program. That recently 4.5 BILLION dollars from people never convicted of crimes. A person has to prove his innocence to retrieve his confiscated money/property in civil forfeiture.
Historical documents show that up to ninety percent of Nazi arrests were because the "suspect" was reported by a neighbor, family member, or fellow worker. The Gestapo could never keep track of everyone on their own.
You see it in America today. Your tax dollars are used by the NSA for ineffective random perusing. CIA pays informants, just like the FBI. The Department of "Homeland" Security encourages snitching.
People are generally not caught because of "intelligence" or "analysis" as shown on TV. They are caught because someone reported them or someone got paid.
See sources in comments section.