I humbly differ from most of the feedback given so far. I'm not entirely sure if you're asking if you should differentiate IP's for your "Money Sites" or your "Backlink Assets". But either way, each one should be diversified on both IP and any other associations (Webmaster tools for example).
It's obvious that you should use different IP's for your backlink assets so I wont get too much into that. If a site has a set of backlinks coming from seemingly different sites, but all happen to be on the same IP, this is a major footprint flag for Google and you're likely to get quickly penalized.
About money sites, put them on separate IP's to spread out the risk. Put them on separate Google accounts as well. When Google penalizes a site, it also takes a look at the other sites related to it, either by IP or WMT tools account. Just recently I had a potential client come to me who got penalties on every single one of her money sites. Was she doing shady backlinking? Nope. One site got negative-SEO'd which flagged her. Then the other sites got dinged for "thin content" for being affiliate sites. If she had been on different IP's, this wouldn't have happened.