Even though you didn't have the money, did you identify specific companies that were worth investing in? Did those companies succeed, or was it others with similar ideas?
Edit: let me give you a simple example. In late 2005 I proposed an investment to a wealthy relative: buy $100,000 of GOOG and $100,000 of BIDU. Any loss would be covered by me as debt, to be repaid over the next 10 years, with a stop-loss at -50% ($100,000). Any gain would be split half and half. Hold it for 10 years, then sell. Unfortunately my relative didn't accept. Baidu did 30x in 10 years. Google did ~6x.
This is a bias that a lot of investors often make ...
Seems to me like you'd want to buy 25k worth of call options at a 50% strike price. The options would cost 25k and would reflect shares worth 50k. You get exposure to 50k of shares on the upside, but your loss is capped at 50k total, which is twice as good as your deal. All you need to do is pay interest.