What would be the best car for a working musician?

That would depend on what you want/need it to be able to transport. You could be a whole band with a drumset, a Bass Guitar, acoustic/Electric Guitar, and a microphone stand plus all your sound mixers or you could just be a musician who plays only acoustic and sings... Good high-capacity cars aren't exactly cars, but vans. Not passenger vans, but those with what is like a small room in the back. This could hold at least a drumset and a bass + guitar. Otherwise, if all you need transport is a guitar or something, just get anything with a backseat ;)