If I am using common app, can I submit my applications and send my recommendation letters later?
Your LORs are sent by your school, not by you. You will notify your GC of the colleges you are applying to. You submit your app and notify your GC that you have done so, who then submits all the relevant info to the college. As soon as your LORs are written you can ask for it all to be sent to the college. Not everyhting has to arrive at exactly the same time. The college starts a file with all your info and adds to it as it receives more info, such as tests scores, transcripts, etc…