The DeKalb County Sherriff's Deputies start at about $33,492 per year and move up to $51,281 after 5 years (http://theblueline.com/feature/ILdekalbcounty2.html). They enjoy 33 days off per year after 6 months, partially paid insurance, paid overtime, paid training, and uniforms. Illinois Conservation Police enjoy paid vacation days, sick days, personal days, and holidays; overtime compensation; uniforms, equipment, and vehicles; life and hospitalization insurance (http://dnr.state.il.us/law3/CAREERnew.htm). Starting salary is $3127/month; after a one year CPO certification the salary increases to $4136/month with an excellent retirement/pension plan. Illinois State Troopers start at $48,192 per year but require advanced training to apply (www.isp.state.il.us). FBI Agents start at about $45,000 per year and can make as much as $120,251 after twenty years (http://www.payscale.com/research/US/Job=FBI_Agent/Salary).
There seem to be certain disparities in pay between agencies. For example, note that the city police make far less than the most of the other agencies. State troopers and university police start higher than FBI agents.