IOS app: marketplace/buying and selling

Im looking to build a marketplace app targeted towards college and school students. Similar systems to Poshmark and Depop, but more modernized and emphasis on college/school students allowing them to input the school they attend to connect more. Buying, selling, shipping, prepaid labels, and apple pay/credit debit systems, owner (me) takes a percentage out of every sale and reviews enabled. Pickup feature included as well. I do not want to copy either of the examples I gave, I want a similar concept.