Both the bellows and the keyboard look a wee bit small...
I'd sure want to play it or one like it before bothering.
Sounds like the buyer bought it and couldn't play it so assurances about 'playability' are rather meaningless. And inexpensive melodeons can be really awful. To me, the a Hohner 'pokerwork' which has been carefully set up and perhaps modified a bit are the minimum standard for 'playable' instruments.