Johnson and Malnati studied data for all multifamily property sales in Denver’s core neighborhoods in 2013. They found prices have increased an average of 89 percent over the past two years. Under Colorado law, all real property (land, buildings, improvements, etc.) must be re-appraised every two years. This occurs in each odd-numbered year. The good news is that in most cases, owners will be able to raise their rents to cover the increases in property taxes.