"15,000 CAVE VISITORS A YEAR

GROSSING $200,000 A YEAR

NETTING $75,000 A YEAR

$500,000 FOR CAVE AND 27 ACRES

$725,000 FOR CAVE AND 70 ACRES that also has an undeveloped cave on it" http://arkhaven.org/arkansas_real_estate.htm

$75K / year net on a $500k property isn't bad at all (~15%). With a bit of work the property could have even more potential.