WordPress best solution shared theme for consumers and businesses (two url’s one instaltion)

What would be the best solution for a wp (cms style) site containing a sub site
for consumers and businesses.

I’ve made a wp theme and its almost finished. In essence its gives you two choice to visit as a consumers or as an business.

Both have the same theme style but differ in some content used out of the wp database and some static content used. (so you’ve got two headers.php and different article categories for both optins)

Now I’ve got it working by using a switch statement in the index.php in the theme file. All works fine but the url’s you’ve get don’t look very professional.

I would like to have it worked like this: www.domain.com –> gives you two options
one brings you to www.domain.com/consumers/ the other to www.domain.com/businesses/

I cant get this to work because for instance the articles use www.domain.com/articles/bla/etc.

So what would be the best way to achieve this? I’m thinking about:
-Multiple installations sharing the same database (dont like this idea because you’ve got more maintenance)
– setting it up in the .htaccess if this possible and how?

thank you for any advice or solutions