Google is looking for good content that interests people and keep them interacting on your site, they are less concerned about them being on the same IP, if that was the case, then all the people on cloudflare would be fucked, which isn't the case.
If your really worried about it, throw them onto cloudflare and all of a sudden they will all be on different IP space
If your looking for only traffic, then the suggestion to nofollow is best, especially if your linking from every page on the domain into your money pages. Might want to link to your money pages within a single post with a follow link, so that you still get some seo juice from your assets!
And as with all things in life, moderation is best, do not make dramatic changes to your domains, do it slowly over the next 6 to 9 months!
