Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) saw no harm in a man giving a garment to another man and saying: "Sell it for such-and-such; whatever you get above that is yours."
This too would be by way of mutual consent, not by way of a binding contract, and Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الإجارة / 11656