In our RMSS game, the GM requires that we are taught new spells and new skills, but not for improving existing skills. There are not a lot of skills that no one in the party has, and there is even some spell teaching within the party, but occasionally we have to go outside the party. E.g. the fighter did find a cavalry trainer to learn mounted combat, and my character needed a teacher to learn a weapon kata. The cavalry trainer did cost money, but also became a new contact for the group (a retired knight). The kata did not cost money, since it was through existing contacts, but in a sense was paid for by my character training a bunch of other students in more basic martial arts techniques (so for a couple weeks he came in battered and bruised every day), really just as narrative (we were in fast time).
We have spent much of the campaign traveling, so it would have been challenging if such lessons were needed every level. For spells, we allow players to purchase a spell with DP but even after leveling they can't actually use it until it's taught. That gives some flexibility about when the lessons actually occur.