Is anyone interested in Co-registration sign ups, co-regs?

Does anyone here do that or interested in doing it? It's like a cross sale, but for a free join. When someone signs up to my site, at the bottom is a prechecked box that they would like a free membership to your site as well. This isn't a cross sale, no credit card info is collected, just name, email, their favorite niche, age, etc.

If you are interested let me know and how much you looking to pay per a free join. Looking for both adult and mainstream company's. Please leave a way for me to contact you as well.


Thanks
Johnny