The first thing you must do when you have signed a contract to buy a property, especially where there are professionals involved in representing the interests of either party, is to lodge a caveat to protect your interest in the property until settlement. A caveat will stop the vendor from selling to someone else or encumbering the property without notice to you.
When you’re selling land, you might have a potential buyer base in your backyard. It’d be peculiar for one homeowner to buy their neighbor’s home, but it’s not so weird for a neighboring farm or another nearby landowner to consider buying the property that’s just next door, so to speak. It could be your neighbors have been looking to expand their farm for some time now. You selling your land provides a mutually beneficial opportunity.
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!