Is it common practice or 'decent' to upvote every answer at own questions?
I mean, the people taking the time finding an answer and typing it, should get some points I would say? As long as the answer is correct of course.
No, not generally. People are expected to answer anyway. They only should get upvotes for good and correct contributions. "taking the time finding an answer" doesn't always imply that it's a good answer that deserves upvotes. I've seen enough users type up worthless garbage that was upvoted anyway because "they just tried to help".
This is the crucial point. Don't blindly upvote people for "This doesn't work, but here's an upvote for trying to help". This won't help anybody, giving a false impression to visitors who think that an upvoted answer actually works, and it encourages people to post wrong answers without trying, since they might score reputation from them after all.
So, only upvote answers that are helpful when you see them. Do not upvote every answer you get, if you're unsure about how it helps solve your problem or if it's just plain wrong.