I'd take that deal in a heartbeat too. 

Trouble is different areas need different property taxes.  I lived in San Diego, huge property taxes, big city with many complex needs (and really wasteful government, but that's another story).  3% probably wouldn't cover needs there. Now I live in rural New Mexico, not so much needed.  3% would be too much.

The other trouble with fixing property taxes until a sale is there becomes a huge incentive not to sell (CA Prop 13) and property values shoot through the roof.  Now you have very wealth old home owners not paying much tax, and new prospective buyers having to foot nearly the whole bill.