301'ing How Related Should the Domains Be?

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?

I do.
Ideally you want your 301 domains to be as closely related as possible. It wont do you any good if you redirect to Penny Stocks site a Dog Training domain just because most links to "dog training" domains will be irrelevant to penny stocks hence - useless.

It is all about relevant links - if domains you will 301 to your main site are irrelevant to your niche, you might actually hurt your site more than help it.

Just my $0.02

Appreciate the feedback, FatSteve.

Frustrating. Finding a lot of semi-close but not close enough domains

You only need to add high relevant content and get every page indexed with the new content.Do a decent backlink campaign so the primary keywords are directly related to your existing niche.Keep adding high quality,relevant content.Use majestic or a similar backlink checker until you start seeing your main keyword as the primary keyword then 301.

PR won't usually carry unless you make the content super unique and build high pr links to the domain you will be 301ing.Age is the one thing that will always carry however if you get enough high pr backlinks you might well keep/improve the existing pr but I'm not sure you benefit from the full pr.

@cloakndagger2: Thanks, that was sort of what I was getting at.