As we mentioned, one of the most popular real estate tools is zillow.com's instant property valuation. Just type in an address and in and you get a property value. It even charts the price ups and downs, and shows the last date sold (including price) and the property taxes. There are other sites that provide similar tools such as house-values.com and home gain.com. Unfortunately, many people use these estimated values alone to justify sales prices, offers and counteroffers. However, these are only rough estimates based on a formula that incorporates the local county sales information. These estimates can swing wildly over a short period of time and do not appear to always track actual market changes, which are normally more gradual. In addition, these estimates do not automatically take into account property remodels or renovations or other property specific or local changes. This is not to say these sites are not useful. In fact, they are great starting points and can provide a go...