Hi
You are looking for a website similar like OLX and Quikr, where people can post the items they want to sell and buyer can choose and contact the sellers. Should work for both IOS and Android, Need APIs and database as well, full architecture.,Integrate a payment gateway if required etc.
I have read your project and got your requirement.
I have some questions regarding the project.
Let me know if you have some time to discuss the details further.
I have already designed & developed many websites. Please check my portfolio to view my previous work.
Please check my reviews.
Looking forward to hear from you.
Thanks & Regards
Mrinal Bhuyan