I've seen a lot of great advice on 301'ing a high PR domain to a low PR money site to help boost the PR on the lower PR money site but one of the pieces of advice invariably given is that the two domains should be related. For instance, if you're in the fitness niche the 301'd domain should be in the same niche as the receiving domain. But how closely related should those two be? Just as an example, if my niche is Oklahoma real estate and I purchase an expired PR4 domain that previously hosted a Oklahoma news site, are those closely related enough? Or, what if I still had the same Oklahoma real estate niche and I purchased an expired PR4 domain that had been for a Florida reality company? Does anybody have any experiences/results they can share regarding how Google treats scenarios like this?