Hi everyone. This is my first post

I've got an offer on the table to make maps for a published product (an adventure module for an RPG). This is my first cartography-type job.

I don't know what size the maps will be on the printed page; I've been told some of them might be as big as "poster size" which is I assume is 17"x22" or A3. Not sure if "poster size" is a term of art.

The original maps themselves were made on Letter paper but might change or require a little more space than that. (I.e. the client's hand-drawn maps didn't have to worry about margins.)

So I'm trying to figure out what resolution and size to make these maps to work on. I guess I do 300 dpi 17"x22" so that they can be printed out on posters if it comes to that, or shrunk down to Letter size if needed.

Oh wise Cartographers' Guild, am I on the right track here?