Many north-Texas neighborhoods financed roads, water, and sewer through a Public Improvement District or a Municipal Utility District. A PID is authorized under Texas Local Government Code Chapter 372. A MUD is a political subdivision under Texas Water Code Chapter 54. Either one can add a line to the tax bill on top of city, county, and school taxes.
The amount is specific to the district and the property. It is on the county appraisal district account and in the subdivision's public documents. We do not publish a typical PID or MUD rate, because there isn't one number that fits Frisco and Prosper.
Lenders include those charges when they estimate the monthly housing payment and the escrow. If the first tax bill after you buy is higher than the bill the seller or the builder showed, the escrow can change. That is a tax-assessment event, not a rate-lock event.