Cool thanks. If I write down one of the addresses today but won't be able to actually do anything tomorrow. Will the address change by then?
I'm using the qt-client and adresses can be used as often/long as you want, I don't see any reason why it should be different for Electrum.
Some clients are giving you a new adress everytime to increase anonymity, but the old ones can still be used.
It's different for some online sites, they may use different adresses every time you want to charge your account or something.
Once I make the deposit and the money goes into my wallet, I will be able to start purchasing correct?
You have to wait a short time for the transaction to be confirmed at least 1 time.