Need help on keyword/domain phrase for business

Hi Guys.
I need some help with the following.

I have a health product which I'm about to launch and I want to attract people looking to either become distributors or setup their own business.
I will offer an opportunity for businesses to market the product in a City or State in the US before going international.
My problem is that as part of the web package I want to set up a 1st page listing for a particular "domain name and keyword phrase combination" i.e Bakers in Utah

Being the health industry, there are hundreds and thousands of queries each day as the industry covers such a wide spectrum.
How can I narrow down my keyword so that it encompasses most quiries.

E.g

If the subject was Plumbers then I would simply use a keyword/domain phrase such as "plumber in chicago" or "best plumber in chicago"

My product covers almost every ailment/illness/health category out there and I'm stuck on choosing a phrase that would 'catch' most queries plus.

People type in...
Warts cure.
High Blood pressure.
How to cure a yeast infection
Diabetes problems.....the list is endless.

So how can I find a 'General' search term so that I could operate the same term for everyone in their different areas i.e

If the best phrase was 'health products'
then I would use the same for all areas i.e health products in boston...boston health products...best health products in chicago etc

Any ideas please?

Thanks