I think the best way to earn a relatively steady income per day, should be mining. It might not be advisable these days, mainly because of the increased difficulty, with the last halving. But it is one of the only options I can recommend, in which you'll get a sure income per day, steadily as you said.

It is advisable if the country that you live has small electricity fees. Unlike here in the philippines mining bitcoin is not profitable because of very big electricity fees. The bitcoin that you will mine won't be enough to pay your monthly electric bill. It is possible i think for rich people here who can buy solar panels and through that mine their bitcoin but it would require much money though. A common people can't afford that.

And also we need to consider the type of weather condition because its better to mine in a cold place thats why all devices that was use for mining have enough cooling system so that it will not affect the good performance of its device.