Mail Help

Ok i currently use hotmail as my e-mail service since all my friends as school use it with msn messenger, i like how its internet based so all my mail doesn't take up room on my computer. my question is: im not sure if it will work but i want to sign up for a free AOL account and use that email address to register with a hotmail account so i can use msn still, also i will be able to use built in mail app that mac os x comes with, will this work and does the mail app save your mail and take up space on your computer or is it internet based. thanks for the help!