Automatic Monkey said:
Technically it is other investors' money. It comes from the brokerage house, which borrows it from the Fed at a discount just like a bank does. So the brokerage is an investor in your margin account because they make a profit on the rate difference. But the brokerage only lets you put it at risk under their terms, they know exactly what you are doing with the money and will terminate the agreement (with a margin call) when they see fit.
This is unlike investing in AP's because the investor isn't constantly monitoring the money, and the investor can't come take it out of your pocket any time they want to. The AP could just disappear.
I agree on the "technicality", but that is really reaching for the bunch of banana's there AM.
The money you receive on Margin is not based on your qualities, looks, AP, honesty, how you play, your skills, etc.. You can be the biggest jack ass loser put on this earth. It's based on the value of your securities/assets and they (the brokerage) can make a margin call at any time, although usually they do not unless the value of your assests have decreased below the required ratio.
I haven't had the experience of another AP or investor backing me, but I would have to say that they can pull out at any time unless there is a written agreement stating otherwise.
but there's no reason to continue this conversation or this thread... we've gotten off the path and have all answered the OP's question.
BJC