What makes an aircraft old? I have flown Boeings older than the Jetstreams. J32's built in 1991-1992 are not that old and many have very low cycles on them and are Ex-American Eagle aircraft. The 1900D's I've seen are high time just ask Great Lakes, they need more and can't find any that are good. EMB-120 or Saab 340 cost a lot more and if you only plan to carry 15, well the Jetstream is the way to go.
I do hope they plan on paying the crew better.