I've read that it's possible to purchase an Oyster-based Travelcard in
advance. For instance, I can buy a 7-day Travelcard effective Sunday on
Friday.

If I were to do that on a brand new Oyster, would the £3 deposit be
waived? That is, if I'm only going to do a bit of travel on Friday and
Saturday, if I, on Friday, obtain a new Oyster with a Travelcard
effective Sunday plus a PAYG balance (to cover my Friday and Saturday
travels as well as extensions during the Travelcard week), would I also
have to pay the £3 deposit?

Thanks.
--
David of Broadway
New York, NY