I am removing an existing dilapidated enclosed rear porch and replacing it with a new three-story open wood porch. It is a typical rear porch, serving as a means of egress, and also has a small area for a table and a couple of chairs.  It is costing over $20,000.  This will be an improvement for the three adjoining 550 square foot 2 br unit in Wicker Park, Chicago.  The units are not rehabbed, but upgraded.  I am trying to get an idea of how much I can raise the rents when the current tenants move-out.