Tenants can rent a farmhouse or other piece of property without hiring a professional. Real estate brokers typically work to connect real estate buyers and sellers; they don't typically work with rentals.
Several websites allow users to search for rental properties. Craigslist offers a wide range of classified ads, and Zillow allows people to search for property for sale or rent. However, some owners might not list their property as a farmhouse; searchers might have luck looking for words such as "farm" and "rustic." It's also important to learn about what rights tenants have in a particular area. Laws might require the landlord to provide certain infrastructure or repairs the farmhouse doesn't have.