Is it with a reputable company? Will you be trained properly, and will they do the required prof/recurrency checks? Is the salary acceptable? Would you have to pay for your rating, or would you be bonded? Do they operate other, larger types (ie is there scope for advancement?) And if so, is there a believable timetable for this? What would the work entail? Do you think you would handle/enjoy the contract lifestyle? (This can be a real problem if you have a long term partner/spouse) Could you get some comments from guys who work for the company already?
Those are just a few of the questions I would have to ask myself or the company concerned before venturing forth....it depends how keen you are for a change. For me, I was lucky enough to go onto a multi turbine on my first contract job. A 'Van is a great aircraft, but it doesn't exactly pad the CV in a big way. Still, it's certainly a step along the road.