You do not need to sell your kids and move to Colorado. Steve and I have worked with many climbers who are in your urban situation. What it takes is some minor creativity and some major motivation and discipline to make the most of your limited terrain options. In fact we will very soon have a series of articles on the website showing how a fellow urbanite made the most of tall buildings to climb both Everest and Cho Oyu without supplemental oxygen within a few weeks of each other.
The principles described in our book are applicable to hiking up real hills or hiking up the fire stairs in tall buildings. You brain will know the difference but from a training adaptation point of view your legs can’t tell the difference.
I hope this helps,