The reason for my question is that I bought a property in August 2010. I painted inside and out and put up a picket fence. It is rented for $850 per month. The assessed value for 2012 is now 100% higher than what I paid for the property two years ago. Although the property should be worth more now, it sure hasn't gone up 100%.
File a timely appeal of your value and present your sales price and some recent comparables to the assessor. If he is unwilling to reduce the value into a range that you believe is appropriate, take that same argument to the local board.
The assessor does not give you enough time to get an appraisal done. I received my fair market value letter 2 days before the appeal deadline. I have cash sale within 2 years, which should be enough. It surely didn't go up over 100% in the last two years. If it did, I would sell it in a heartbeat.
Yes, that is typical. I don't know how much you spent on upgades, but I still calculate well over a 10% return (excl maintenance). I bet you get the valuation knocked down - like you said you have a transacton within 2 years. Good luck.