Does Amazon hosting is good for dynamic adding / removing space/cpu with API?

If I want to do build web service that charging users Is this strategy will work for me ? Suppose I want to build web service that will charge monthly, now each time user will sign up I will programmatically buy more hosting space and cpu . when the user will sign-out I will programmatically remove this space Of course this is for the total hosting bill . can I do that with Amazon ? or do I need other web hosting ? Thanks