I would avoid fake ads on ethical grounds alone. I try to treat people as I would want to be treated. There is already too much bad information and noise on the internet, which undermines the overall quality for everyone.
The best way to find cash buyers is by using a real estate agent.
The best way to find cash buyers is to deal in the type of property and price range of the typical cash buyer in your area and you will not need an agent that will pull even more money out of your pocket.