Build a parking app only for 2 cities in my area.

I live in Queens NY and live close to Brooklyn NY. I want an app for my city Richmond Hill aka zip code 11419 and a few surrounding areas about a 3 mile radius from here whereby users can signup and they can put where there car is on the map. The app will have a time when the car will be leaving that location. Basically this app is so that people can go on and see when a person is leaving that parking spot. I also want it so that if a person is leaving a parking spot they can set the time they will be leaving. The app will then show the time the person is leaving 30 minutes before they leave. This is an idea I have and really want to make it for my community where parking is tough. If it is easier to just do all of NY then let me know but really want to focus on my city. My budget is tight as this is just a thing I am doing for my community.