Joe:

This summer, I "transitioned" from guitar to banjo.
Not your regular 5-stringer, but a vintage (although not expensive/valuable) tenor banjo, that I was given by an elderly friend of mine who didn't play it anymore.

After a bit of searching on the 'net, I tuned my "new" 4-stringer to "Chicago tuning" which is exactly the same as the 4 high strings on a guitar.
That made finger positions and chord names very easy to learn, although my fingers still tend to "look" for those 2 missing strings.

I did the same thing for a ukulele.
I bought a baritone so I could tune it the same as the banjo.
One set of chords, 3 instruments. <grin>

Good luck!
LLOYD S