Hi ,
I am happy to see your requirement , you will also be happy to know that i have a similar product already with me developed by me , my product has following modules :
1. Admin Panel : Admin can create category, sub categories , Approve Reject vendors , set delivery locations and lot more.
2. Consumer Android App: Consumer can see nearest vendors , categories , subcategories , products with respect to specific vendors and place order.
3. vendor consumer app : Vendors can add their products , set price quantity and receive orders.
please let me know if you need demo of the same , i would be more than happy to give you the same also please not the cost and time i have mentioned are just to get in touch with you once i have exact details actual cost and time will be mentioned.