Your property taxes are usually reset based on what you paid, and the mechanics depend on your state. In California, Proposition 13 ties your assessed value to your purchase price and then caps annual increases at 2%. A below-market purchase, like a fixer bought well under comparable homes, is generally assessed at the price you actually paid rather than what the finished home would be worth. One caveat: on an off-market sale that never hit the open market, the county assessor can ask for documentation, such as photos or contractor bids, to justify a low price. An MLS-exposed sale is usually accepted at face value, because other buyers had the chance to bid higher. In the other 49 states there's no Prop 13 equivalent, so homes are generally reassessed on a regular schedule, and the current owner's bill is usually close to what you'll pay. To estimate your number, look up your county's effective tax rate and apply it to your purchase price. In California this is trickier than people expect, because part of the bill is a percentage of value and part is fixed voter-approved amounts, so simply copying the prior owner's rate produces a wrong figure. Also budget for a one-time supplemental bill, the catch-up charge that arrives after the county reassesses to your purchase price. When in doubt, confirm the current local rate with your county tax assessor.