Your only chance is to mine new or less popular coins with low difficulty and trade those for BTC. It is possible to make some nice money that way. When protoshares came out i mined 50 of them (about $1k at the moment) with a core 2 quad within 2 hours. I had similar luck with other coins. You just need some luck and a good nose
My suggestion, if you really want to get into crypto coins without investing some real money, is: Take a lot of read on crypto coins and even more time for thinking about what you have read. While you do so mine some of the rather easy to mine coins, join some alt coin exchanges and use the coins you have mined to bet on other coins. That way I have made a few $10k this year despite the fact that gambling, ehm.... i mean trading, never was my thing and my hardware is not really suitable for mining (never was into gameing so all my graphic cards are rather low end). I know some others that made a few $100k this year, just with a good graphic card and the right nose.
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