For the sake of argument, let's say that the Promise program will be the panacea for Davenport that its backers claim it will be. People will flood into the city because they've been promised college tuition, vocational training, or (if they're in the military) a homestead grant. Enrollment in the Davenport Community School District will reverse its nearly-two-decade-long trend of decline - thus ensuring a greater amount of state education funding, which is distributed on a per-pupil basis. And the increased aggregate property value will bring new riches to city government and the school district through property taxes, thus allowing them to lower the property-tax rate.
Even if all that is true, the backers of the Davenport Promise have structured the program all wrong.