INVOICING iphone/android/web Simple database+web-service based app

Hello! I need to develop a very simple app for ios, android, web; I just have no time and my poor abilities could make this quite long if I do it myself! So: It is a simple invoicing system. It shall enable the user to register his data, and send invoices on his behalf to a third party person details submitted in a form into app. The platform should consist on: -A database ([login to view URL]) with a table for users, another one for clients, and one for admin (to debit one at a time the invoices purchased, and keep logs). -Connection to web service, get response (pdf invoice): Simple SOAP, REST, .NET,etc. -Email pdf to third party upon user approval; acces natively. -Invoices in Mexico need to have an embedded qr code from client´s data. [login to view URL] can handle this. We need to enable a payment module. I want to sell invoices individually /bulk. I am not sure wether the apple appstore will accept or not a web payment service, as the invoices can be seen as a digital good for in-app use (also web browser use) in which case we would have to add a in app payment module, or force people to buy credits out of the app! Workaround ideas are very welcome. I want to keep this as simple as possible. I would like it to be under the scheme below, not having to work/pay a lot (starting up alone!!); and because integration with web apps is very easy, so it can create a multi platform app in little time. [login to view URL] I have a few other projects, and if price-timing-quality balance shows up positive, I would probably propose a long term collaboration. Each proposal will be carefully evaluated. Let´s work together!