Fiqh-us-Sunnah Volume 5, Hajj and ‘Umrah, Fiqh 5.110A.

One may sacrifice any animal one chooses. The Prophet (peace be upon him) offered a hundred camels as a supererogatory sacrifice. The minimum number of animals a person is obligated to sacrifice is one sheep, or one-seventh portion of a camel or a cow (by sharing one-seventh of their price). A camel or a cow may be sacrificed on behalf of seven people. Jabir said: “We performed Hajj with the Prophet (peace be upon him), and we slaughtered a camel for seven persons, and a cow for seven persons.” This was reported by Ahmad and Muslim.

For a sacrifice to be acceptable it is not necessary that all the partners should be of one mind. Thus if some do it for the pleasure of Allah, while others do it to obtain meat, it would still be valid. The Hanafi school, however, holds that a necessary condition for sacrificing is that all the partners must have the pleasure of Allah in mind while offering sacrifice.