No - we've sold plenty to investors, but have not had a deal where the buyer was using private investor financing.  But - wait - we did have a "Buyer" who had a wealthy friend purchase the home on their behalf - but the home was deeded to the purchaser, not the intended occupant.

Many times, we build our business on this.

Many times, different types of deals and all worked out well.

I had buyers bring me a pre-approval from private investors once, but it didn't work out.

When time is of the essence many investors will utilize hard money loans or private funding. The goal is to be in possession of the property as quickly as possible, fix it and put it back on the market for profit. 

To some buyers...private funding is the only option when institutions refuse to lend due to strict regulations. Wasn't Bernanke denied a loan? His strict regulations back fired...

Yes, I've had a couple of these with no issues.

My wife and I have recently utilized a Stated Income Loan financing.  We inherited a home with a Reverse Mortgage and it needed to be paid off or sold.  The value has gone up by about $80,000 since the refinance.  The rate we paid, due to zero documentation, was about 9%.  This may not be a private lender but it is the type of loan you seem to be referring to.  Let me know if you need this type of loan.  They have a lower rate with a bit more information but we used none.