Enquiry about a plugin needed

Hi,
I am new to wordpress. I am developing a website which will have and sales. for this i am looking for a plugin which will be comfortable to me to develop. Here my requirement is i am giving a member ship to merchants. so they can also able to add their products into the site through log-in into their account. And admin will have the all permissions. The store, sales tables should be in my database not in other stores or third parties.