First, I hate faxes so I think your company just jump out of the 19th century (when fax was invented) past the 20th century into the 21st and send you information in a form you can actually use after you receive it. You can ask and you might get lucky.
Second, Vonage and others support fax numbers in two ways. First, you can get the limited time plans for $10-$15 per month for 500 minutes and pay an extra $5-$10 for a fax number. Each carrier handles this differently. Vonage, for instance, charges an extra $10 for a fax number.
Almost all the broadband phone companies also offer a business line model, usually for $35-$50 per month. This usually includes a separate plug for your fax along with a separate phone number.