How much money is to be made exploring?
There are charts that show the various amounts to be made scanning different objects. There are also bonuses for using a Detail Surface Scanner, and for being the first discover. There is a lot of information on this sort of thing floating around the forums.
The TL;DR : you will not make as much money exploring as with other professions.
But, really, the way to find out, is get the biggest fuel scoop you can find, strip down your ship to light components for distance (using your own preferences for whether to take shields, heat sinks, weapons, etc.) and just make a short trip out. Go out a 1000 ly and back in a couple of days. That will give you a much better idea of what you are in for that anything else.
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Do you find flying up to every planet with a detailed scanner is a hassle, or do you not need to?
I tend to be selective. Beyond the obvious (the Earth-likes and water worlds) there are Ammonia Worlds, high metal, and even generic heavy metal worlds can be lucrative if they are terraformable. I also tend to pick up closer gas giants, because they are a quick scan if they are within a couple thousand ls. Likewise, secondary stars in a system.
If money is your primary goal, you might want to consider heading to the neutrons fields in the direction of Sag A*. I've never been there, but by reputations there are billions.