The House Always Wins IV

The House Always Wins IV is a main quest

Synposis
The Omertas dealings are beginning to concern Mr. House and he wants to know what's happening across the street at the Gomorrah. The receptionist he used to pay for info has been tight-lipped, which is even more concerning. Whatever it might be, House wants the Courier to uncover what the Omertas are doing.

Detailed walkthrough
Mr. House asks the player character to deal with the Omertas for Mr. House. The player character can achieve this by completing How Little We Know, or killing all the Omertas. Upon doing either, the player character must then return to Mr. House. If one has previously done either, the quest will mark as completed automatically. House will pay the player character anyway, just to avoid discouraging them. Alternatively, the player character can just refuse to surrender his weapons upon entering the casino and thus turn the Omertas hostile. There is no need to kill any of them, leaving and speaking to House will fail the quest but allow the player character to proceed to part 5. This is the fastest way to pass this section but forfeits the rewards.
 * Completing The House Always Wins: IV will cause the player character to fail Beware the Wrath of Caesar! and Render Unto Caesar.

If one has already finished How Little We Know by siding with Nero and Big Sal, then one will automatically fail part IV when talking to Mr. House, unless the Courier can pass a Speech Check of 50 and tell him the Omertas' plans and then say that the player character infiltrated them in order to gain their confidence.

For more information see the side quest How Little We Know.

Quest stages
Part IV

Bugs

 * After eliminating the Omertas, Mr. House doesn't recognize that they are gone. To remedy this, load a save point before killing Big Sal and Nero, go talk to Mr. House and make sure you go through all the dialogue on what to do about the Omertas. After this, killing Big Sal and Nero and returning to Mr. House should allow you to finish the quest.
 * Without having a save point prior to killing Big Sal and Nero, the quest can be fixed by using the console command . This will treat it as if the Omertas were already dealt with before receiving the quest from Mr. House.
 * When working on Part IV of the mission, there will be an option while talking to the Omerta receptionist that says [Barter x/55], meaning you need at least 55 Barter to choose it. But upon using a Salesman Weekly to raise Barter to 55, the option goes away, and you are left with the [Strength x/8] option or the option to hand over 300 caps. Leveling up the Barter skill does not help.