DO NOT offer equity right away. Marketing/Sales guys are good at selling themselves, but bringing in revenue is tough. Not everyone can do it consistently.

Let them have a stake in the sales (say 10-15%) and make sure it's transparent that sales are coming through him/his efforts. Assume you'll be hiring more on these kind of terms.

Once you see something rolling, you can offer some equity accordingly.

You'll know how confident he is when you tell him there's no salary, only %age of sales he brings in.