can you open a store that has multiple sellers?

[Tika Twine]

can you open a store on market place and allow members of your group to sell their products threw your store?

[Rolig Loon]

If it's an in-world store, certainly, and it's a great idea.  As you wander around in SL, you'll find some excellent stores that are co-owned.  Often it's because two or three creators collaborate in making items that combine their skills as builders, animators, or scripters.

If you're talking about a Marketplace store, the answer is no.  Well, not quite, but only one person's name can be on the shop.  Every SL resident potentially has a shop in Marketplace.  All you have to do is open it.  Your store is tied directly to your account.   All money flows through your personal account -- the same one that you use for everyday things in SL.  Also, anything that is sold through your shop has to get there through your inventory, and remains your personal property until it is sold.

Now, I said "Not quite" because you can share profits.  If a friend gives you her items -- so that they become your items -- you can upload them to your shop and sell them.  And you can designate during the setup process for each item that you want a fixed percentage of the sale to be sent to your friend.  Her creations will be in your shop, but she will get her share of the sales.  See http://community.secondlife.com/t5/English-Knowledge-Base/Selling-in-the-Marketplace/ta-p/700193 for more general information about setting up your Marketplace store, and then read http://community.secondlife.com/t5/English-Knowledge-Base/How-to-market-your-products/ta-p/700181#Section_.2.4 (in particular, the short section about Revenue Distributions ).