Mobile App and Backend Server

Mobile App for IOS and Android: - marketplace app connecting buyer & seller - buyer choses from a list of categories and drills down to individual items - Can choose products, quantity for each product, delivery time & location, etc. - Seller can update profile with products available, price for each product, description, photo, etc - Seller can view order details and accept order or decline order (buyer than has to choose new options) I have a list of items that we would like to include for each user but is still not yet verified by my boss. For now, would to find out how much it would cost to develop such an app and how much to maintain it (hosting fees, domain name registration, etc.)