Build me a e-commerce marketplace app

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. Buying, selling, and shipping features- also including placement for the college or school you attend. Pickup feature included as well. I do not want to copy either of the examples I gave, I want a similar concept though, but emphasizing on school/student selling app.