I am unsure about if they test you for getting a green card so i cannot answer that.

As for blood testing, if he abstains for 3 days he should be able to pass a blood test drug screen.

I am going to need his height, weight, excercise habits to make an accurate assessment of how soon he will be clean if he were testing via urinalysis.

It is worth noting for those who smoke sparingly they can potentially be clean in less than a few days.