Sci-fi novel about an alien servant traveling the galaxy with a con-artist "genius" master

I'm trying to identify a science fiction novel I read a while ago. Details are fuzzy, so apologies in advance — here's everything I can remember:

- It's centered on a creature (an alien) who travels around the galaxy in a spaceship as the servant of another alien. Both main characters are aliens.

- The master belongs to a species that's widely regarded as highly intelligent, but they're really kind of con artists / frauds.

- The servant constantly puts himself down — very self-deprecating, low self-regard throughout.

- The twist is that by the end, the humble servant turns out to have done far better than the "superior" master he'd been serving.

- The tone is serious, not comedic.

For timing, I think it was published somewhere between the late 1940s and the mid-2000s.

Unfortunately I don't remember any character or species names, what the servant looked like, exactly when I read it, whether it was a standalone or part of a series, or the specific details of how the ending played out — just the relationship and that final reversal.

Any ideas? Thanks!