Richard, old chap, whenever have the worlds of music and art ever presented anything other than puzzlement to people of logical minds?
Accordionists, like every other sentient being, are a very varied bunch and that which suits one person may be an anathema to another.
The initial question, from an aspiring accordionist, fits into that concept of "How long is piece of string?", to which a rsponse might be: "What kind of string?"
My answer? - Get hold of a squeezebox, any kind of squeezebox, one which is in good physical and operating condition and which sounds sweet to the ear, and play with that for a while; in the meantime seeking out and listening to as many kinds of associated music and its performers as practicable.
I'm at that beginning stage, so I advise from a position of beginners' uncertainty.
From a purely practical viewpoint, buy whatever is in general circulation in the region in which you live so that when you finally decide on a particular style/format/tonality etc. you can, if needed, easily dispose of the initial purchase with ease having eventually found a more suitable instrument, if that is the case.
Unless you are lacking in versatility and adaptability, moving from one style/shape/form/system to another is not going to be too much of a problem.
And just be content to know that most top musicians started serious learning at a very early age, building on a foundation of inherent talent and with lots of familial encouragement; and many of them are not routinely playing the on kind of instrument/s on which they began their musical journeys.
It's all a bit of an adventure really and, for me, the joy is in the discovery and learning, far more than the ultimate performance ability.
