Is it mandatory to buy a house via a licensed broker?

[Aditya Bhate]

Wanted to know :

If a good deal is found via any of the following:

Wholesaling Vs MLS Vs Birddog Vs Seller Financing

The realtor or a broker's role comes only when buying house listed on MLS.

Wanted to know can someone directly purchase a good deal from a wholesaler or found visa bird dogging or passed on via seller financing.

That way we could eliminate realtor fees and would be a win-win for the buyer and seller.

(This question was asked to me by my friend who is getting a great deal via the latter methods)