Zoho is a brand that has comprehensive suite of products that can be availed under one subscription (Zoho One) or as individual products such as Zoho Books (accounting software), Zoho Analytics.
What is great about Zoho is that it has a free plan for most of its suite of products that might be what a small business all needs. This is different from say QuickBooks or FreshBooks that offer free trial but no free plan.
So you can refer Zoho through your affiliate links to your network of small businesses with limited budget. They will benefit from the free offerings. In case your referred sources upgrade, you should get affiliate commission (though I have not checked how exactly at this time).
Zoho affiliate program is operated in-house. Apply for Zoho Affiliate program here: https://www.zoho.com/affiliate.html
Zoho Consulting Partner program is for those who are interested in providing implementation support, and one can join only either as affiliate or consulting partner.
Become a Zoho Consulting Partner here: https://www.zoho.com/partners