The general rule is that you cannot sell what you do not possess, because the Prophet (ﷺ) told Hakim ibn Hizam, "Do not sell what you do not have." He also prohibited selling foodstuffs before taking full possession of them, as Ibn ʿAbbas reported: "Whoever buys foodstuff should not sell it until he has taken possession of it." The wisdom is to avoid gharar and to prevent profiting from goods whose delivery is not yet guaranteed. Recognized exceptions exist, such as salam and, per many jurists, istisnaʿ (a manufacturing order), where the description and terms are fully specified.
Evidence — the daleel
On deen2u
Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.