Mobile Apps

Building an app can cost a lot of money, the problem is that if you want to make your app usable on iOS and Android then you will need to create two separate apps. To keep the cost down you could create an HTML5 Hybrid app which works for both thus keeping the costs down. However hybrid apps aren't always so effective because they don't feel as good as native apps.

Develop with ionic or flutter platform, and build hybrid app for android+ios.

For back end database use "back4apps.com", they offer a free plan that's practically all that you need on starting phase.

For push notifications use Onesignal+Firebase

Let me know if you have any more query.