To be honest, i had no idea on how to correctly stream nor buy songs on iTunes, so i had to make some researches and here are the most important tips i found (c.btschartdata & @BTSxSoutheat) 

Steps to buy a song on iTunes:

* You can login with up to 10 accounts with the same device (be it an iphone, ipad or laptop).

* If you don’t have paypal or a credit card, you can buy an itunes gift card from stores like walmart. You will only be able to use a gift card in one account. 1 gift card per account.

* You can create as many accounts as you would like online at https://appleid.apple.com. 1 email address per account.

* You don’t need to have an apple product to download itunes, you can download it in a windows computer too.