Find me that town too all my buyers will flock there.
No seriously property taxes are essentially based on the towns total assessed value of land and the actual structure multiplied by various "tax rates" depending on the municipality. The larger the property and the larger the home in square footage (and bedrooms/ baths/ finished basements etc), it follows taxes will be higher.
Towns that have more large commercial/ business tax revenues tend to have slightly lower residential taxes since commercial properties pay a significantly higher rate and increase the tax revenues, but then you are in a more urban or semi urban area.
Unfortunately NJ has the highest taxes in the country. Your focus can be lower taxes in just about any town, but its probably smarter to figure out other priorities that would apply to your situation like commute/location, schools and price range, then look for homes that fit your budget which still could be taxes a bit higher (or lower) than your $9000 limit.
There are several modest and affordable homes in South Plainfield with taxes under $9k.
I would be happy to speak to you for a no obligation chat about your needs. Give me a call at 908-675-0167.