I would advise against monticello. My cousin-in-law's husband is taking some criminal justice courses and applying for police jobs in the area. He says there is a lot of drugs in the area, domestic violence and assault.
To give you the low-down on Monticello - the area has a brand new casino there and is experiencing some growing pains. While the cost of living appears cheap, the taxes in Sullivan County are disturbingly high. The schools are not the best. Ellenville NY is also not a great place to live, niether is Port Jervis.
If you are interested in the area and obviously wanting police jobs I would suggest a few different options. Middletown is the county seat of Orange County and there is the courthouse and Sheriff's office there. A couple good places to live in the area are Minisink Valley (just west of Middletown), Greenville NY, and the areas to the west of Middletown that do not have Port Jervis school districts. The housing there is not as cheap as Monticello but the taxes are less and you have better schools and access to better jobs.
Eastern Orange county brings a lot of job opportunities for security/police work. You should find the pay to be pretty competitive. I have heard starting base salaries as low as 56K/yr and as high as the mid 60K, with some correction officers I know making 6 figures a year with OT. That salary would enable you to live anywhere in Orange County you choose. Just so you know, that is info from people who have applied for jobs, so I have not researched it myself, but it sounds like a reasonable salary for this area.
Stewart ANGB in Newburgh NY
http://www.dmna.state.ny.us/jobs.html might have some DOD security jobs open as well.
Also FYI- there are 2 major correctional facilities across the river in Dutchess county. Downstate and Mattawan sp?. There is a Psychiatric facility for the criminally Insane in Goshen NY. There is also a prison in Wallkill NY on rte 208. I am sure there are others, those are the ones that pop off the top of my head.
Not sure if you are moving from out of state, but some needed info if you are: One catch is that in NYS if you bring your firearms here upon your move you are in violation of the law. You cannot possess handguns here without a permit. You are expected to leave them with a FFL back in your state, get your CC permit (took DH about 4 months and you must appear before the judge) and then have the FFL dealer send the handguns to you. Not sure if they speed things up a bit if you are in a career that requires you to carry, they very well might.

Of course you can call the town clerk in Middletown and speak to the pistol permit officer there who can advise you of the latest and greatest procedures to make sure you are doing things the right way.

That was the procedure 2 years ago when we moved here but things can change.
If you are moving from another county in NY i am unsure of the procedure. I think you have to give a change of address at the Town Hall and file some forms but the Pistol Permit officer can let you know.
Some really great school districts are Minisink Valley, Wallkill, Monroe Woodbury, Pine Bush, Valley Central. Warwick is pretty good as well. you can look at the report cards for the schools and get a feel for the schools that are experiencing some difficulty.