Write an Android application for Online Biology Tuition

I would like it to be simple with nice & elegant design so that students can chat with me and book a class with me and pay for it through app. (Payment gateway or pay pal through app) Please note that I am only the single teacher for teaching Science to primary grade and Biology till college grade in this app. Registration can be done only by student from all over the world with email or phone no. whatever you think will be best for me. registration from tutor is not required as I will be the only tutor in this app. Student should be able to select Science or Biology Subject. Then options for boards like cbse/ap/icse should come. then class etc. Instant doubt through chat with payment per question. Student should be to post pics from their book or screenshots etc. Students can request for a class with me which is done on Skype. Class can be instant or scheduled for say 15 mins/30 mins/45 mins or 1 hr or it can monthly tuition or unlimited instant doubt clearance etc. Please place bids accordingly as I am House wife and freelancer and single tutor and I will be owing my Mobile App. Its is my start-up venture.