$0, 你要清楚房东的工作是什么

You are obligated to provide a livable housing.  That is plumbing, electricity, water, heating, gas, window, doors...

Paint has nothing to do with livability (legal word: habitability).  If they didn't like the paint, they don't have to sign the lease. 

You don't even have to allow them to repaint the walls.  你需要提高业务水平，出租房不是只收房租啊。

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