No, how he makes serious money in the muggle world in 1991 Britain may require actual research.
“Hi. See this gold bar I have in this box? See this silver bar I have in this box? Buy gold if the exchange rate falls below X, and deliver it to Y address. Buy silver if the gold exchange rate goes ABOVE this rate, and then start selling the gold. These bars? Oh, yeah. They’re seed money for the operation. We’ll talk once you’ve depleted the funds for this operation.”
“Hi. See this gold bar I have in this box? See this silver bar I have in this box? Buy gold if the exchange rate falls below X, and deliver it to Y address. Buy silver if the gold exchange rate goes ABOVE this rate, and then start selling the gold. These bars? Oh, yeah. They’re seed money for the operation. We’ll talk once you’ve depleted the funds for this operation.”