Mortgage payments are nominal (dollar) amounts. So as prices rise with inflation, the real amount of the payment (the payment measured in today's dollars) declines. For example, if your mortgage payment is $20,000 this year and inflation doubles between this year and next, your mortgage payment next year will be just $10,000 measured in today's dollars.
Unlike your mortgage payment, homeowners insurance, property taxes, maintenance costs and condo fees typically keep pace with inflation. That's why, unlike mortgage payments, they remain constant through time in our reports. Moreover, if you specify that your house will appreciate in real terms (i.e., relative to inflation), we have your homeowners insurance and property taxes rise accordingly at the same rate through time.