Confused About Mortgages Do I Need To Take Out A Buytolet Mortgage If I Want To Rent Out My Property

I am a first-time buyer looking for a flat in Surrey.
If I decided to rent it out straight away, Would I need to get a buy-to-let mortgage?
If I Live in the flat for a while And Then decided to rent it out do I need to change my 'standard' mortgage to a buy-to-let?
How Much Should I Be charging rent in order to cover more The Mortgage insurance / service charges etc.?