American Traveling to China for a Week

Hello! I am an american college student, and I am entertaining the idea of vacationing to Shanghai or Hong Kong over my winter break, and I had planned on staying through a place on airbnb. Also, I fly non-rev so my flight plans being scheduled aren't usually until like 1-2 weeks before, and I wanted to ask about how long it takes to file the applications without the rush, and then also ask how much around it would cost just to come for like a week on a L type, having never been to China before!