Abstract: A system and method for collective-based property valuation with a mobile client provides a user interface to a device that allows parties viewing a property to enter estimates of the property's value. Fields for a number of property attributes allow viewers to select scaled values indicative of supply and demand in a subject market. The values are used to create new cost-per-square foot and cost-basis valuations of the subject property. The accuracy of the home valuation improves with each additional valuation, resulting in valuations that truly reflect supply and demand in the subject market. Separate values for house, lot, estimated sales price and current market value are calculated and displayed. A past sales price engine estimates a current sales price based on a past sales price and the average appreciation for a neighborhood. A user interface feature allows different users to enter rating data in succession.