Mobile Application for IOS and Android

I am looking to build an application for posting used machinary.
The application should allow the users (sellers) to have their account, and post their available used machines on the application (photos, description, price, telephone number,etc.)
The application should also allow the users (buyers), to search for keywork they are looking for (example: generator, exacvator, etc.), with model number, year of manufacturing, etc.
The application main page should allow the user to easily select the machine category that he is looking for (like: generator, building machine, etc).
Complete details will be done on the go while developing the app.