Once it is sold to a third party the insurable interest that the owner has on himself is gone
Insurable interest has nothing to do with who owns the policy. It is the beneficial interest that must be established with the issuing carrier at time of underwriting. Once the policy is issued the beneficiary can be changed to anyone, even Tony Soprano, and the carrier cannot do anything about it.
If I sell my own 100,000 term policy to you for $70,000 (the numbers I've seen most often show a 30% discount), you own the policy but what insurable interest do you have on me?
A 30% discount would indicate death is almost certain to happen any day now.
Generally the policies are sold at a 50% or much greater discount.
Insurable interest is no longer the issue but transfer for value rules do apply.