But the monies paid by the trainees will cover part of their day-to-day running costs of the firm.
It's a good way of adding a bit of security, but not exactly great for their reputation. I imagine their attrition rate of people that go full time must be over 80%.
I think you may be being a bit optimistic... if they need money from trainees to cover costs then it wouldn't seem like their trading business actually makes much money if at all...
Reality is that these sorts of operations aren't as feasible these days anyway - as far as discretionary trading in futures is concerned there are far far fewer people doing it now compared with 10 years ago - the established firms in this area make most of their money from their clearing/brokerage side... some have systematic trading teams too or fund them/rent office/desk space to them in addition to clearing their trades - the grad programs have mostly either been scrapped or massively scaled back - charging a fee to learn some technical analysis, get taught about economic releases and go on a sim for a bit is utter BS...
You can replicate that experience for free in your bedroom - give CQG a ring and ask for a free trial... its unlikely to get you very far, you're very very unlikely to find an edge staring at charts and taking a few directional punts on the S&P.