As a 30 year Realtor, Ive used many sources to try to find comparable sales. We go 12 or 6 mos back. Occasionally, I paid tax depts by the hour in other counties to find properties that have parameters of a subject property in that area especially if it was not in an RMLS to which I pay dues. I often ended up consulting with a Realtor in another RMLS or referring out.

I found it very difficult to use raw data unable to ascertain features like weatherization and amenities. One problem is that one seller may have bought, invested 70k in improvements before selling, another may have bought to flip. Details, whether landscaping, hardwood vs laminate floor, paint, foundation, age, type of roof, siding, foundation often are provided to allow a correct property value. Age of heater/AC or ecological features would also be unknown. Devil in the details.

Info in RMLS that only a licensed Realtor/appraiser can access allows a more accurate analysis of price. The crystal ball knows all, I kid!