This relation does not only apply to NCAA and NFL teams though. For example, take Tropicana Field the host of the St. Petersburg bowl and also the home of the Tampa Bay Rays of the MLB. Also Back in the Day, the Cincinnati Bengals and Reds played in the same Riverfront Stadium. In 2014, the Cincinnati Bearcats play all of their home games at Paul Brown Stadium since Nippert Stadium is undergoing renovations due to be completed by 2015.
Personally, I like the idea of sharing stadiums because if I were short on money, I would have to simply share a stadium with another team.
Riverfront Stadium (Cincinnati)