Police Salary depends on the individual departments themselves.
Generally speaking, once someone is hired and begin training they receive a wage, however it's at the lowest level.
Every department's starting salary will be different, and depending on the size / location of the department, you may see a wide range of starting pay rates. Obviously, depending on the location of the police department within the US, costs of living will vary.
Areas such as California will have a high cost of living as compared to some other areas in the country, and departments in that area will have to offer their officers a higher pay.
After all, as much as people may dream of working in law enforcement, if they cannot afford to live in the area that they are working, they will just as easily leave for another department.
Benefits such as medical plans, vision care plans, and dental plans are all usually provided to officers, but like salary / wage, it can vary across the board as well.
Normally, these benefits do not extend to new recruits the way that they would to an officer who has completed the training at the Police Academy and have started on patrol.
Once training is completed and you have graduated, a salary increase takes place, with another increment following every year until you meet top pay.
Whenever a contract between the city and the Police Union ends, a new contract is negotiated, and generally speaking, salaries increase slightly.
Benefits can also improve, but with the current recession, this may not be the case. Negotiations are likely going to become quite fierce, and wage freezes are also a distinct possibility.
Officers will likely encounter situations of overtime which will increase the pay from the base salary:
Changes to different units may also include incentives like larger clothing allowances.
A change in rank (promotion) will also increase the annual salary of an officer.
It's difficult to give a blanket answer as to what the average salary is, but this section will attempt to provide info on specific departments...