It actually varies a lot by state. In Florida, where I used to live, it was $25-50k lopped off the value of the house before taxes were assessed. Proportional to house prices, this was a lot.

In California, where I live now, its only $7k. Proportional to house prices here, it barely qualifies as lost pocket change that fell out of your pants and is rattling around the washing machine.

Of course those laws sometimes include other provisions, such as tax cap portability when you move (sometimes only for old/disabled/etc, depending on the state). The limits on tax rate increase might sometimes also be tied to this.

I honestly don't know the details. I just think the idea is right. Homeownership by individuals is desirable but it's not desirable if big companies with deep pockets buy up all properties. We should have policies that put the home buyer with an average salary at an advantage over the big guys.