Being an affiliate partner and a joint venture partner you are leveraging other affiliates contacts and subscribers, this could ultimately boost leads and sales for you and your affiliate campaigns.

To find a joint venture affiliate partner you need to be looking for affiliate niche products in the same niche as your product if you have one, then once you have a handful of potential affiliate partners, you contact each one and send them a well thought out affiliate proposal - Something along the lines of "I'll promote your product if you promote mine wanna do it?"

Why not start off with all or most of the top marketers that are celebrities within your niche market, you know where to find them! on the world wide web of course or just Google