This isn't something that is automatically set up within Shopify, but we do have apps available that you could use in combination to start up your site! These apps are:
Multi Vendor Marketplace will allow them to post on your site, and you can use Draft Orders to charge your realtors.
Hope this helps,
Hi guys, I have a similar idea and because I couldn't find any themes on shopify for real estate on the themes store I had to search on the internet until I found this template on "Template Monster" :
The page of the theme http://www.templatemonster.com/shopify-themes/50794.html#gref
The theme in Action http://www.templatemonster.com/demo/50794.html
The theme looks OK for me but I would need to get a varification from shopify experts that the theme would work on shopify platform,
I would only change the button "Add To Cart" and the Qty box with this box :