So, my daughter recently got married. We have a joint credit card (I'm co-signer) that we got her several years ago to start to build her credit. Her new husband doesn't have any credit cards or any credit score data really. So, they want to start trying to build his credit score.

What helps them build a good credit score together better?

a) He gets his own first credit card, probably pretty low everything since he has zero credit record.
b) He becomes joint on her credit card (I get off ... has to happen either way... it's time and she doesn't need me to co-sign anything anymore!) which gives him a higher limit and everything and it's both their names.
c) something else?