The question came to me: What would the cost-of-living be for an NPC living in the Keep on the Borderlands?
B2 doesn’t seem to list the rent for the private apartments. A private room in the inn is 1gp/night. That’d make about 30gp/month. On the one hand, a private apartment ought to cost more than just a private room, but hotel rooms cost more than apartments, right? I’ll just stick with 30gp/month.
The Basic Set price list (which happens to be reproduced in B2 for quick & easy reference) gives 5gp for 1 person-week of unpreserved food. So, that would be about 20gp/month.
So, 50gp/month for food and a place to sleep.