In Kentuky, starting pay is about $30,000. You should be able to find other state's starting pay on their government personnel website.
In Ohio probation officers can start of at 32,000 a year.
I did a search in Trovit's salary tool and found that the average is $81,000. I will attach the link below so that you can see the salary tool and search for probation officer job listings as well.
HOW MUCH DO PROBATION OFFICERS GET PAID IN A YEAR OR MONTHLY.
$66,000 a year.