Need Advice for a Web Page That Promotes Local Businesses

Okay, let's say I've noticed a house cleaning businesss website in my town which looks nice. It seems to be a nice company.

Is there a way I can help to promote her site and her business on the web by setting up a search engine-friendly page for house cleaning in this town and then linking to her site? Let's say if I put her on the page as an exclusive.

Should I set it up as a "pre-screened" referral sort of site, or would that be necessary? Would the search engine hits be good enough if I found the right keywords or would I need to promote the site elsewhere (as I don't have a bunch of money to invest and I want to keep it as simple as possible)?

And how could I find the best keywords that get the most hits? If I did a site only for housecleaing, what else could I put on there aside from just her? Would something like automotive be better (or medical/dental)?

I need to know the best strategy.

Would I be better off setting up a community sort of site with exclusive businesses on there? I simply want to offer people like this something so that a lot of traffic is driven to their site and they could just pay me a modest amount.

Also, what other ways could I find business for business locally, as though I'm finding the work but they're doing the work?

Your thoughts, please.