> does anyone know, how long would it normally take an average person to
> learn pali enough to be able to start reading the suttas without that
> much difficulty?

Can you put in a solid 2-3 hours a day, six days a week? Have you
studied a foreign language before? Can you get a hold of the best
learning materials available? If the answers are yes, I'd guess 3-8
months. You'll already be reading suttas earlier than that, but it will
probably take that long before you are reading them on your own without
needing to struggle with every sentence.

If you've had Latin or Greek in school it will go faster.
If you've had Sanskrit it will go a LOT faster.
Chanting Pali at temple services and memorizing the 'iti pi so'or other
such texts can even be a help.