It is interesting. One important difference is if the broker knows they have to pay the broker they are probably more likely to due their best to keep a tenant if they have to deal with it. The landlord also wants to make as much money while having a marketable rent - so its not like they don't care if they have to raise rent to cover expenses.

I still think having this on a platform where a company is making a flat $250 fee (or whatever) is extremely scalable for the company and would benefit both the landlord and tenants.