Well, you can even invest 10$ in some coin and still profit on trading (or just by holding or participating in ICOs) but the profit is minuscule. You can definitely start with small amount but the profit is directly proportional to it--smaller, for small capital, vice versa.
There are many ways for making money in cryptocurrency market. If you have big investments, it is much better. You can buy crypts and hold them for long time. You can also trade with your coins. But if you have no investment you can make money in bounty and signature campaigns. This platform provides you the opportunity to make money without any investment.