The following method works on the PC, PlayStation 4 and Xbox One copies of GTA 5. However, in single-player story mode, a change of clothes and a stolen police cruiser can land you a job with the Los Santos Police Department. In GTA 5, there's no police academy and no applications you can fill out to work in law enforcement. Getting a job at the GTA 5 police station is a little different than it is IRL. Instead, you can be a member of law enforcement, working against those very people.
When playing Grand Theft Auto 5, you don't have to be one of the characters pulling a heist.