Well, there are no standard definitions or situations, so I wouldn't just assume that there is no business structure or infrastructure to an imprint, but if you mean an artist-owned label directly under a major as opposed to a full-fledged indie with distribution, then signing with that imprint/artist is akin to signing a production agreement with a producer, except there is a stipulation for options/number of albums to be delivered. If you have a good lawyer, you may get a "key man" clause, meaning you can get out of the obligation to the parent label if your imprint guy or gal is no longer in the business.
GJ