You can mine or do some freelance jobs, maybe checkout sponsors on the forum or try to invest money and buy some alt coins aswell if you know what your doing. countless possibilities to earn some bitcoin!
One thing is sure, isnt a easy way to achieve 1 bitcoin free, without invest nothing besides time. But its possible, last days altcoins market are being pumped a lot, soo this may be the easy and fast way to try, but there are some risks as well.
As you said it is right, earn the 1 bitcoin it is very hard if you never invest any amount, so same situation also happen in altcoin trading, because you need a amount to buy the coins than you do trading, and i know trading is best way, but in my experience, altcoin trading always give you short profit,
It doesn't mean that i do trading with a small amount, even i buy a CJ with my near about 2 bitcoins but i still waiting to make the profit.