Some people after you help them, just go away.
Some people after you helped them just go away.
Some people after you’ve help them just go away?
The first of these is correct, except that it is missing a comma:
Some people, after you help them, just go away.
The second and third both seem to be an attempt at:
Some people, after you have helped them, just go away.
"you have" can be shortened to 'you've" with no change in meaning.
When using the auxiliary verb form "have", the main verb "help" must be in a past tense. so "have helped".
In this case, the meaning of the two sentences is essentially identical. The second one perhaps emphasizes what has happened in the past more, while the first is more generic and covers both past and future. But this difference is very slight.