I am in the process of launching a beta for my niche "invite only" dance marketplace. I would like to collect recommendations for "referral marketing" tools. For example, I want to be able to invite Sally, and then Sally can email up to five of her friends, who then individually invite 5 of their own friends. Any low budget/free tools that provides this capability that I should look into?
Thanks so much in advance for your tips, tools, and insights!