How one can earn a living say $4000 per month from PTC sites is it possible ?

I wouldn't trust on PTC sites to make a monthly residual income. It might be possible but it will take some time to arrive there and furthermore your need more than one Program which will remain in the market and not disappear after some months or a year...

For the rest I agree with what was said before: lots of ACTIVE referrals (rented or gathered by yourself) which will click the ads as you daily!!

is there any sep by step free guide to make this happen?

BY REFERING FRIENDS AND LOGING DAILY IN THE SITE FOR READING MESSAGE

This is possible, with active direct or rented referrals.

and though you can have a great flow of web traffic