In the 4th case, it doesn't cost anything, but you can lose up to $30k if SPY goes to 0 (very unlikely). More likely is SPY ends up lower at expiration than your trade price, and you pay that difference.
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These are worst case scenarios, and calculating the return is more complicated for anything other than the 1st cast. If the market moves in your favor, the leveraged instruments will make you much more money than the 1st case. As you can see, there are many ways to use your cash just with this one investment.
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These are worst case scenarios, and calculating the return is more complicated for anything other than the 1st cast. If the market moves in your favor, the leveraged instruments will make you much more money than the 1st case. Even though they have expirations, you can continually roll them to future dates to simulate a buy and hold. There is some active management required to keep the positions other than the 1st.