Artist Pension Trust
 

I got an email about this and it's an interesting concept, though sending a non-portrait piece would likely make a piece easier to sell. Mind you, I am not endorsing them and know nothing about them at all.

They wrote: APT is the first product that gives emerging and mid-career artists the opportunity to plan for long-term financial security. This company creates a unique pension fund in which artists contribute their artwork, which is held for a number of years, then sold, with most of the proceeds going into the trust. This is an invaluable service to artists and their families.

http://www.artistpensiontrust.org/