This will be good for beginner pilots to make some cash. I used to attend a flight school and knew some graduates making minimum wage as entry-level flight instructors, and there are stories abound of commercial pilots not doing much better (Google "LAX ghetto"). They're basically glorified bus drivers. By cutting out all the mega airport overhead (airlines pay the airport for facilities, terminal use, baggage handli…
You can't make money this way since you can not be paid more than your pro-rata share of the flight costs. By definition that means the money you get from passengers is going to be less than what you paid to fly.
Suppose you and 3 passengers take a flight where the direct costs total $400.
Your pro-rata share of $400 is $100. Your passengers could pay you up to $300. $300 is more than $100, so you can clearly be paid more than your pro-rate share.
The FAR says you can't pay LESS than your pro-rata share. In this case, you aren't.