It depends on the kind of return you're expecting. I would say that most people buying right now to make a quick buck will be disappointed. But long term, great things can happen. And you might not have to wait more than a year, since we are very close of having Lightning Network.
This is true if you gonna play in long term any amount is good for investing in bitcoin, also many are want to play on short with bigger amounts of investment with fast and bigger returns after sell.
In any way most are play on long term no matter the time they buy what they can when they can and income is for sure.