@McQuant Right! I've also heard that these prop firms can also sometimes function as market makers and initiate the other side of the client's trade by buying or selling a security. I don’t know if it’s true.
It is unfair to lump all Prop shops into one bucket. As TickCom said above, anyone offering "trainee trader courses" especially those expecting you to pay for them, are not worth looking at. But there are prop shops that have been around since the trading floors closed, that are reguated, are members of the exchanges that they trade on and do offer valuable services. If you are a proffessional trader, looking for a trading room with other professional traders, that offers IT services, compliance services, clearing and settlement services and interactive risk management services then, they are out there.