Joomla, database, component, modul(s)

Firstly, I have no idea which skills it takes to create what I need. Having said that, I can show you an example of a working program: [obscured] /cost-of-living It's a database that holds information about the cost of living in different cities around the world. The database gets fed by user that live in those cities. It's probably takes the average of the numbers that the user input. This database needs to be built and it must be possible to add cities, items (goods) and their prices manually from the backend too. Then I need some modules on the front end that let users choose two cities to compare. publish the prices and give user the chance to input prices. This way, after the initial data input, the database get updated automatically. This will become a very small part of my website. It's just an extra service unlike the demo site i gave you the URL of/ My website is not operational yet. I'm working with Joomla 2.5 I'm serious about the project but I have no idea about prices this is my first time using this service