This is a highly specialized area. I assume he is trying to attract investors. He needs to talk to people who know the market and have insight into his target audience.
If he has a stock broker he might want to start there.
I would try 3 areas. Trade publications specific to the category, general business publications and the business section of local newspapers for counties that don't have viable biz pubs.
I would pick a few in each category to gather information about their coverage of the demographic he's seeking for both the specific counties but he shouldn't limit himself to just those counties if it's an investment there would certainly be others outside of those areas who might be viable. IN reality he probably needs selective regional/national coverage.
He might want to find out if the trade publications in this category have mailing lists that he could buy (most do) which would be more cost effective with higher response rates than a scatter shot approach to the general population of investors. Too much waste which is expensive.
There may also be some websites specifically targeted to that category that have advertising sections that focuses on investments. They would also have mailing lists he could use.
Finally he should look at some direct mail companies that cater to businesses other than consumer facing to see what specialties they offer. He would want to find a list of investors that have shown an interest in that specific category or similar categories. --71.75.xx.xx