The U.S. govt puts out an "Occupational Outlook Handbook" each year with general educational requirements and average wages, etc, for just about every occupation. Here is their entry on firefighters: 
http://www.bls.gov/oco/ocos329.htm#oes_links
Here is a relevant section:
Earnings About this section
Median annual wages of fire fighters were $44,260 in May 2008. The middle 50 percent earned between $31,180 and $58,440. The lowest 10 percent earned less than $22,440, and the highest 10 percent earned more than $72,210. Median annual wages were $44,800 in local government, $45,610 in the Federal Government, $25,300 in other support services, and $37,870 in State governments.
Median annual wages of first-line supervisors/managers of fire fighting and prevention workers were $67,440 in May 2008. The middle 50 percent earned between $53,820 and $86,330. The lowest 10 percent earned less than $40,850, and the highest 10 percent earned more than $108,930. First-line supervisors/managers of fire fighting and prevention workers employed in local government earned a median of about $69,000 a year.
According to the International City-County Management Association, average salaries in 2008 for sworn full-time positions were as follows:
Position	Minimum annual base salary	Maximum annual base salary
Fire chief	              $78,672               	$104,780
Deputy chief         	69,166              	88,571
Battalion chief         	66,851 	        81,710
Assistant fire chief	65,691        	83,748
Fire captain	                60,605        	72,716
Fire lieutenant     	50,464        	60,772
Engineer             	48,307        	62,265
Fire fighters who average more than a certain number of work hours per week are required to be paid overtime. The threshold is determined by the department. Fire fighters often work extra shifts to maintain minimum staffing levels and during special emergencies.
In 2008, 66 percent of all fire fighters were union members or covered by a union contract. Fire fighters receive benefits that usually include medical and liability insurance, vacation and sick leave, and some paid holidays. Almost all fire departments provide protective clothing (helmets, boots, and coats) and breathing apparatus, and many also provide dress uniforms. Fire fighters generally are covered by pension plans, often offering retirement at half pay after 25 years of service or if the individual is disabled in the line of duty.
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