Accurate sales data and rehab costs in Denver?

[Graham McBain]

Back in Arizona all of the sales price data was available from the county assessors office so it was easy to see what people were paying for deals even off market(most of the time). What is the best resource here in CO to find those details, especially off market. 

Any insight would be great! I'm building a DB of the opportunities in my market and I would like to get the best data possible so I can make fast/informed decisions. To that end I'm also hoping to get a more accurate picture of rehab costs so I can make sure the deals I source make sense! 

ALSO: If you're interested in deals in the Clayton/Cole/Whittier/City Park North area I'm an experienced Door Knocker/Marketer and would love to be your wholesale huckleberry.