A comparison would be how much value will adding a bathroom add to a house? I've shown that adding a second bathroom to a 3 bed/ 1 bath home can be worth $50k for specific homes and neighborhoods. I definitely wouldn't say adding a bathroom to any home will increase its value by $50k or even what an average value is. It depends on the house.
Even though the property isn't in a special flood hazard zone, a basement can still be a source of flooding and moisture problems. In our mild winter area, people generally prefer having views of their gardens (consider Eichlers - windows cost more than walls, the big windows weren't a cost savings).
Home values for zip code 94306 can be viewed at http://julianalee.com/zip-code/94306-statistics.htm
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Basement square footage is not considered living space when the city of Palo Alto determines how much allowable square footage can go on a given lot. However, buyers often do take that in consideration when deciding what they feel the house is worth.
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