Web service for android social networking app?

I am developing social networking app on android.Rough idea of my app is that when user launches an app it will get all users of this app in near by location.So for storage purpose of users data I want to use web server. I don't have an idea what is best way to start with.Should i use Amazon web services ? (S3,Ec2) I was surfing internet got these buzz words. Please guide me what is best approach for database storage ? Should i write my own server api ? or What ?

These are some general things you will have to do:

1. Buy some server space where you can host your server (this is the amazon ec2, etc). If you need a fancy domain name, buy that too, and map it to IP address of the server that you brought (optional).
2. Setup a db of some kind on this server to store your data (msql)
3. Write wrapper web services (php, jsp, etc) which will expose apis to access your data remotely. For security reasons, you should also have some authentication using some token passing mechanism.
4. Access the data on your server remotely using the APIs you created in the web service.