Selling without a realtor

[Christopher Olsen]

I think they call this a "less than arms length transaction."

My brother and I will, hopefully, be selling our inherited house this summer. The neighbor across the street has expressed an interest in purchasing it. He wants it for his niece to live in apparently, and apparently can pay cash. 

If we reach a deal before putting the house on the market, can it all be done without realtors getting involved? Are there any other savings in such a deal?

Risks? Pitfalls?