Consideration is also sought in the obligation of the donee to use the donation for the purpose specified.1 But this obligation does not attach until the donation is paid in, and is nothing more than the legal duty resting upon the donee, which can not be a consideration,2 and is held not to be a consideration for a subscription.3 If the donee undertakes more than the mere application of the donation to the purposes thereof, as where it promises to give "free tuition to twenty students forever,"4 a consideration exists. If, in return for their subscription, the donors are to receive something of value,5 such as corporate stock,6 or land,7 a consideration exists, as this is an executory contract of sale or something equivalent thereto.