What is the penalty for vandalizing someone's personal property?

Likely, what you would be charged with is criminal mischief. That charge can be a misdemeanor or a felony. The cost to fix the damage will determine whether the case is filed as a misdemeanor or felony. A Class B misdemeanor carries with it a range of punishment of up to 6 months in jail. A Class A carries a range of punishment of up to 1 year in jail. A State Jail Felony is 6 months, up to 2 years. A 3rd degree felony can be anywhere from 2 to 10 years in prison. There are likely a lot of facts and circumstances that would allow you to avoid serious jail time. However, you need to hire an attorney, and that attorney will need much more information, both about you, and the situation, in order to better guide you.