Limit user type

Hey,

I’m setting up a closed site (invite only).
I have to types of users:

1. venue owners – they only sell.
2. agents – they only buy

I need the best practice to allow:

* venue owner can only see their own listings
* venue owner can post sales (listings) but can not bid
* Agents can see all listings.
* Agents can’t post new sales.

Thanks.