To "come by" means "to come to have" or "to come to get" here:
At least he comes by his problems honestly.
How did you come by that haircut?
Where did you come by that haircut?
Here, it means "to arise from" (i.e. to come to be as a result of):
Great ideas don't come by brains but by guts.
Success doesn't come by brains alone.
Come conveys the idea of events-as-they-unfold. The statement and questions in the top set speak and ask about the circumstances that led up to the thing. For that reason, to my ear, Where...come by...? is slightly unidiomatic whereas *How...come by...? is idiomatic.
These are actually different verb phrases, and would be spoken with different parsing rhythms and intonation patterns.
Success does not come {pause} by brains alone.
How did you {come by} that haircut? { } = spoken as a unit without a syntactic pause between.
No, they do not quite have the same meaning.
"You are getting close to..." implies that the person is moving. For example, they are searching for the sign, but they are not "getting close to any".
"You are close to..." implies that the person is still. They may have been searching for it, but they are not currently "close to" any signs.
Also, your sentences don't make very much sense. Here's what they should be replaced with:
"No sign you are getting close to it."
Replacement: "There is no sign you are getting close to" (it was removed from the end of the sentence, and there is was added to the beginning)
Better Replacement: "You are not getting close to the sign"
"No sign you are close to it."
Replacement: "There is no sign you are close to" (it was removed from the end of the sentence, and there is was added to the beginning)
Better Replacement: "You are not close to the sign"
For example, If my friend was searching for a sign that I placed, and was walking around and could not find it, they might ask me for a hint. So, I would say "You are not getting close to the sign". (My friend is moving, and is either getting closer or farther from the sign as he moves)
For the second sentence, if my friend was about do do a flip, and wanted to make sure that the sign was not in their way, they could ask if they were close to it, to which I would respond "You are not close to the sign". (My friend just wants to know his surroundings, he's not currently trying to get closer or farther away from the sign).
"getting closer to" should only be used if the subject is moving and wanted to know where the object was in relation to them. "close to" should be used if the subject is not moving, and doesn't really care about exactly where the object is
Best Answer
Not is acting as an emphatic. It means that the speaker wouldn't let them do it if they didn't pay the person they are speaking to. It is particularly strongly emphasising that that is a strong reason not to let them.