I produce a web show and wanted to incorporate some local talent as part of the music for the show. I have met with the band already and we have a verbal understanding of what we can both do for each other.
For now there is no charge for their music, and I have agreed to promote them on my website and show.
In the future I will have DVD's for sale and have agreed to pay a percentage of the sales to the band as a royalty. I was wondering what a fair offering would be?

Whatever you can get! However
Whatever you can get! However, for one of my long time clients, I pay them 50% of the net profit - and we do enough business that this works for both of us, while I have another who does less business, and it's a 70/30 split in his favour. In this case he also pays me 30% of his own direct sales - so it works and we're all happy.
Eric, get it all in writing.
Eric, get it all in writing.