If the immigration placed a hold, even you pay the bond the money will go to waste. If the bond is set at 5000, you can find a bailsbond and you will have to pay like 500-600 and the bond will be posted. Now here's the legal loophole; after a bond is posted for a person they should be free within 24 hours. If the immigration puts a hold on you, that means they will come and get you. So if the immigration doesn't pick him up after 24 hrs of posting the bond, you can hire a lawyer and he will file a Habeas corpus and he will walk out of the county court.
But if the immigration does come before 24 hours they will detain him and proceed with removals. Out of fear or whatever your friend should remain silent(that's your right) and not sign any paperworks.
If you were to post the bond do it on early Monday morning.

Good luck