A storekeeper may not be set up for half the profit, nor may money be given with which to buy produce at half profit, unless he gives him his wages as a laborer.  Hens may not be set to brood at half [profit], nor may calves or foals be assessed at half [profit], unless he gives him the wage of his toil and his feed. But calves or foals may be accepted for half profit and raised until they reach a third of their growth; and a donkey, until it can bear [a burden].