Well I know what it was like for me as a young female driver with a brand new mini 13 years ago. It wasn't cheap then and I doubt it's got any better.
If it's going to be his car and he is the main driver it will be a killer. Unfortunately anything with turbos on which a lot of the newer engines have to try and make them more 'efficent' are a bit of a flag to insurance companies with young folks. As are premium badges.
Adding you and the Mrs will help lower the premium. Unfortunately you'll not know the kinda costing until you get some idea of quotes. He could even do that just now on a hypothetical not yet bought the car but seeing what the offering would be with 1 years NCD.
I know my cousin who's 22 has a 1.6 A3 TDi convertible, has 4 years NCD, lives in Curmunnock and pays £700 a year for her insurance. And she's been a student living at home.
Hopefully he'll get something sorted but I'm sure you'll make sure he doesn't make any rash decisions.