I want to build a e-Commerce website for my Super market.

I want a platform to add and delete products listed in my e-Commerce website as per my wish. I should also be able to apply disscounts and offer coupuns to customers (for the listed products).User should be able to login his details, the platform should store the information and also the COD should be available too with all other modes of transaction. Also let me know the budget for development of an Android app only and also the budget for developing both Android and iOS app.