How much does the content of surrounding pages matter in SEO?

Last summer, we created a quick house sale website - http://www.quickhousesale4me.co.uk/ - onto which we tagged a "rent flats in Ipswich" page. The site didn't have too much priority at the time so we didn't do two separate sites.

Now, however, circumstances have changed and we wish now to promote both the quick house sale aspect AND the renting flats page. For the last month or so, I've been writing some articles in my spare time but have so far only had about 12 accepted and indexed - about 12 more are awaiting approval (will update the links club if/whena rticles get accepted and indexed!!).

Would it be better at this stage to cut our losses and create a separate "rent flats Ipswich" site where all the pages on the site are about renting flats - rather than having the quick house sales pages diluting the relevance of the renting flats pages and vice versa? Or would you say that offering a quick house sale and renting flats are sufficiently close in subject matter that we can get away with it? Or does it not really matter providing we get enough links??

Would appreciate any feedback.

Building two sites is an option sure but the two subjects go together and in the eyes of Google the whole might be greater than the some of the parts since a site dealing with both subjects is likely to be more useful for humans than two separate sites.  I think pooling the two gives a greater opportunity to build Authority

If it's done well it won't be a problem for visitors, just make the navigation clear, lots of websites deal with more than one subject and often they're not even as closely related as your two subjects are.

Always a tough decision this one, just been through it on a website project with a guy who does offers a consulting service and sells documents on the same subject and we decided to build one site in the end.

Yes google ranks pages not sites and yes sometimes individual pages can rank independantly of anything else but the majority of pages in the SERP rank because they are part of a larger site.
 
Sometimes when I'm doing keword research I'll come across pages that seem to have no reason to be ranking well, they have no PR, no backlinks and no discernable signals to justify their rank but closer examination always shows that these types of pages are part of a larger more authoratitive site and my conclusion is that the site itself is passing on that authority and causing these pages to rank better than pages that do have their own signals.

It's this evidence, coupled with the fact that the theory about site 'authority' makes sense as a way of determining what's useful to google users and what isn't, that makes me a believer.