Bases and specially base for Challenger850??
They don't care very much about where you live. As stated on their website:
Has to be either Austria, Germany or Switzerland, within 1hr of an airport with scheduled airline service.
Note that speaking German is essential.
Ch850 requirements state 5000TT for left hand seat and 1000TT as F/O.
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They haven't got any Ch850ies yet, but are supposed to get four this yr (June, October, Nov and Dec), along with 4 Ch605s, 2 Ch300s and 2 Lear60XRs.
Edit: their careers site:
http://www.vistajet.com/en/about_careers.php?career=2