Multiply the taxable value of the property by the tax millage rate. You can find both the taxable value, and most often the actual taxes for the property, on the township or City websites. In general, the taxable value is supposed to be about one half the market value - though the calculation is complicated and this can result in wide variances. Most tax rates range from $25 to $34 of tax per $1,000 of taxable value (or $500 of market value). For example, on a $100,000 market value house the average tax would be $1,500 (($30/1000) x (100,000/2)).
Whether the home has been occupied as a primary residence can also impact the tax rate for a period of time up to 1 year for you as well. And finally, some taxing districts may have a lower property tax rate but impose an income tax.
It's best to partner with a seasoned real estate agent and mortgage loan officer who can make sure you understand the full cost of ownership for any property that you may be interested in. Good luck!