They do fairly comprehensive land value + structure value assessments for property tax in many US states. Basically they collect data on every property like square footage of building, size of plot, age of structure, etc and do a regression based on comparables in the area where the real price is known. It's not perfect for every property, but is a fairly straightforward analysis. Individuals can challenge the model's output if it's too far off. The same method could easily be adjusted for rental rates.