Mobile car marketplace (Native Android and iOS) or (Cross platform tools like Phonegap,xamarin etc.)

Background For bid is Project X, which is a mobile used car marketplace that allows users to sell their car as well as browse cars online. For architecture, we are open to suggestions, but the mobile app should be very responsive i.e. some caching should be done locally on the mobile device. Also we are seriously considering using Xamarin as the underlying platform because we would like to build this application across multiple platform quickly and do not want to have the overheads of having too many developers. Compatibility The App has to be compatible with iOS 7.0 as well as Android (Jelly Bean) and above. The App should be usable across the tablets and mobile devices. Inside your description, please state if your bid is for native (both iOS and Android) or PhoneGap, Xamarin etc. I am open to suggestion. Responsiveness of the UI is important, so if you suggest platforms like PhoneGap, please be able to develop the UI efficiently. Sections Browse Cars • Search • Filter/Sort Detail View • Call Now Favorite Cars (login required) Sell Cars (login required) • Upload Pictures • Create Car Ad • Remove Car ad Car Discussion Board • View Discussion • Post comments (login required) Profile Login/ Signup Information Popup Timeline Week 1 - Browse Cars, Favourite Cars Week 2 - Profile, Discussion Board, Login, Signup Week 3 - Sell Cars, Information, Introduction Week 4 - iOS UAT and app store submission Week 5/6 - Android UAT and play store submission If you can do faster than this, that would be best. Other features - Some animation from screen to screen may be required - Data synchronization – caching and more - Optimized file size for APK and IPA build External APIs and 3rd party software - Car Data APIs - SMS APIs - Push Notification API - Analytics SDK - Image APIs (for uploading pictures) Please drop me a chat request for [login to view URL] screenshots. Please include your final bid (i do not want to negotiate bids), I will have the app specifications sent if you are short listed. But please try to be as close to your bid as possible. Please give also, your best indication of timeline. The Data APIs will be provided, but if you have input on how I could set up more scalable backend, it would be much welcome too. This is largely a pure front end development, the design is done, but I need someone to convert my storyboard into UI on Android and iOS etc. Also, this is a long term project build into 'phases'. The next phase will be social integration of facebook connect