The question mark I think hangs over the 'sold him' angle, is that who is going to buy a disabled child? Especially in the 1950s, when you could be arrested for being visibly disabled in public. (The last of the 'Ugly' Laws wasn't repealed until 1974 in Chicago!
Disability Rights Timeline ) I can see a childless family buying a child born out of wedlock to have their own family, but for many children born in this way, disabled or just illegitimate,
you paid the family or baby farmer to take them, they didn't pay you.
The only way I can see money going to the 'birth' family is if he was perfect and desirable as a potential son. And if he was clearly disabled and that was the reason for the 'birth' family's rejection, he wouldn't be perfect. They'd be paying for his maintenance, or paying a one-off sum for him to be taken away. It's the only attraction for the family taking him - much like families today who foster for the cheques, not for the welfare of the kids they take on.
MOO