The 1989 Tax Court case of Carl Stevenson has raised questions as to whether self-employment tax is due on rental income where farm machinery is rented to others (usually children) after retirement or is retained at the time of incorporation and rented to the newly-formed corporate entity.
Harl, Neil E.
"Renting Farm Machinery at Retirement or Otherwise,"
Agricultural Law Digest: Vol. 2
, Article 1.
Available at: http://lib.dr.iastate.edu/aglawdigest/vol2/iss17/1