A somewhat surprising fact about selling real estate is that it can be far more difficult to find a buyer for a piece of vacant land than it is for most types of existing homes. The reasons for this are many, but often they are related to either the location of the land or the amount of work or expense that might be necessary to improve vacant land for a specific usage.
You can also look to certain companies and organizations that have a concentration of people that may fall in the above mentioned roles such as investment companies (i.e. Charles Schwab, Fidelity), financial advising companies (i.e. Morgan Stanley, Merrill Lynch). There may be a higher concentration of people who can both afford and want to build their own custom homes or to build income-producing properties. Try linking yourself to financial advisors who may already know of people who have these types of dreams. This isn't a comprehensive answer of all the possibilities but just some thoughts. Good luck!