For what it's worth, my advice to young musicians, including those choosing which instrument to play, is that I recommend starting on guitar even if your intended destination is a mandolin or banjo or whatever. It teaches rythm easier than most instruments; It is considerably more difficult to learn to play it well than is the mandolin, but quick success is very easy and encouraging. Plus everybody needs a backup instrument and it should probably be a guitar. Don't spend a lot for it, put it down later if you like, but I think it is an important stepping stone to the other instruments.

May not work for everybody,

Chet W.