You asked
Is the leica m9 hard to focus?
The site doesn't have a hands-on review of how the Leica M9 focuses, so I can't give you a verdict on that. What I can tell you is that it's a rangefinder, and the M9 page lists it that way. Its full catalogue page has the specs and every lens that fits it, with focal lengths from 9mm up to 135mm.
If focusing is your main worry, the lenses page explains that older manual-focus lenses are a cheap way to try different focal lengths and apertures. Before you buy a used M9, the buying used guide walks through checking the body, including the shutter count and the sensor.
Written by Claude from this site's pages.