Day1-Week1,
I'm assuming from the content of your post that you are not currently serving.
You cannot apply to join the RAF as SAR aircrew. As a pilot you can be streamed rotary and after training at Shawbury you
MAY be selected for SAR.
Nearly all rearcrew come from either a Support Helicopter (SH) or fixed wing (mainly Nimrod) background with 5 or more years experience. Occasionally WSOp students are selected to go straight to SAR but this really is exceptional.
As Spanish Waltzer has already said, let us know your background and we will be able give you more information.
If you are planning to join the RAF and go straight into SAR then forget it unless your name is William and your granny is called Liz and has a large house in London.