I think any coaching that this type of co-operation provides should be very active, and not just "Go through our training materials".
What your friend suggested sound similar to franchising. It is simple way (but often not cheap) to get started but not that great in long term.
When you apply this to poker it becomes more blurry, but basically it is better business for the stable as long as both parties honor the agreement. So even if you would be a winning player from the start they would skim money of you long enough to make a profit from your work.
1) I do not think so. Playing with someone else's money is like taking a loan for playing. You still have to pay it back, and if this doesn't concern the player then I don't know what will.
I described it briefly so that you would understand what I personally did not like, unless of course you had no experience of cooperation with such funds. This was the very first task, I was required to watch this video and take notes on it. All further coaching there is very active, but not for me and not in my case. This training is good and useful for those people who are new to poker and who have not yet fully understood the meaning and versatility of this game, have not learned to feel it. Before starting cooperation, I corresponded with them for about a week. I told my poker story (I have been in the poker industry for 15 and a half years, of which about 4 years I worked as a dealer, some time I worked as a cashier and administrator, the rest of the time I periodically played, sometimes live poker, sometimes online poker). After our conversation, I was asked the question: "Why don't I play with my own money?" I told him about my series of failures in online poker, after which the coach answered me: "The whole reason for your failures is variance, learn to overcome it and everything will be fine for you." I am grateful to him for this, now I understand that in principle I am doing everything right, I just need to be patient and play a lot in order to overcome variance.
What my friend suggested is not exactly franchising, it is more like a regular partnership. In franchising, a person or enterprise must constantly pay for what works under a certain franchise. I did not have to pay for anything, here, on the contrary, my friend had to pay constantly, and negotiate with many different people in order for this business to exist. All that was required of me was to invest physical labor and spend my time, that is why there was an offer to split the profits 50/50. The principle is exactly the same as in poker funds: you spend time and effort, and the fund takes on the material side and the time and effort spent on your training (for which, again, you do not pay anything). I think in both cases everything is fair.
You wrote: "they will take money from you long enough to make a profit from your work." Well, why long enough? If you are a profitable player, you can terminate the contract with them at any time. As far as I know, this clause is spelled out in contracts in many poker funds.
What can I say about franchising. You probably know what McDonald's is. So this corporation operates on a franchising system. "As of the end of 2022, 40,275 restaurants operated under the McDonald's trademark, 95% of which were franchised." That is, if so many restaurants operate on such a system, then it is beneficial to both parties. I think if you study this topic carefully, you can find enough similar examples. I just never did this, I heard about McDonald's once and now I remembered it when the conversation turned to franchising.