I'd echo Mick's answer but also add that I like to split 'Resellers' into two different buckets for SaaS.

1. Pure Resellers
These folks purchase the SaaS product (to show commitment to selling it) and then spend time re-selling the product. They DO NOT do anything else besides sell and provide referrals. Generally they are commissioned similarly to your sales people, but can provide a discount so they can make their margin.

2. Value Added Resellers (VARs)
These people buy your product, sell it (and get a commission), but then also do implementation for the people they sell it to. The money maker for VARs is being able to charge for professional services (which can often be much more expensive than the SaaS product itself). You should discuss how much they charge for services (you don't want there to be a huge discrepancy in how your product is implemented), but this will definitely vary between VARs.

The exact terms and payment amounts can vary depending on your product but hopefully these two distinctions can help with the way you approach structuring terms.