If they do not have a contract for you to sign, then you shout definitely set out your guidelines for your image usage. i.e One time usage for the said product, additional costs for any extra print run-ons of the calendar, not to use your image for any other product without prior permission by you
As for cost, this kind of depends how many calendars they plan to print and who the client is. If they're a big deal, then you'll be able to charge a good rate. If it's just a local business then I doubt they'll be much budget for images.
You can always ask them what their fee is and then negotiate.