If the agent has not given good advice on this, then here it is.
Your friend needs someone who cares about them to negotiate for them. The agent who listed the property should know what they are doing, and do this as this is expected of them in a property that is upside down in a loan.
The investors does not care about the deal except to try to make some outrages fortune. This use to happen a year or two ago and this contributed to the downfall of home values all around us. Just remember when an investor buys a home in the neighborhood, usually that isn't good news.
So if the deal fails, your friend will more than likely go straight to foreclosure. The odds of the deal going through are next to nothing as most investors want to make at least a 30% gain.
Most banks, will not let a deal go through for less than a 5% loss these days. In fact for the most part market value is the only value they accept.
You would never want to give permission to a buyer to orchestrate the whole deal of a transaction.
Harold Sharpe - Broker
So Cal Homes Realty
California Department of Real Estate Broker License # 01312992