Do you mean margin/leverage trading? well, that is riskier, if you mean money invested by a company for you to trade with, then basically it's an investment, that comes from marketing, either promoting yourself to the company/investor/if the company has a contest etc.
Yes in theory what you say is true, just like anyone knows to buy low and sell high, but the reality is not that simple people know discipline and risk management we are human and always bring emotion into trade, and it can make good money,
but no it won't make you rich if you don't bring investor money or any other term you use, and the required discipline and emotion required to handle a 10k account, and 1mill acc is different. trading your own money, and trading investor money is also a whole diff case, except you are a machine, there is a reason why 95% of people trade is losing money.