Old cameras are like old humans - they all come with age-related problems, some serious, others less so.
There is no denying that the SL range, like all Leicas, are darn good cameras. But they are old. And they use film, which is now niche.
This partly due to how heavy they are, but mostly how expensive they can be when you have to get them repaired. And you will. Unlike my Nikkormats, if one of my FT2s goes kaput I can go online and buy another from Ebay for <$100 - and if the new one gives up the ghost, well, hoo. Ebay is there yet, to the rescue.
Another factor. A friend, sadly deceased a few months ago, bought a new Leica M6 in 2000-2001. Paid AUD $6000+ for it, a fortune then, a bargain now. Very little used. Has sat on a shelf in his home for the past decade. Now about to be sold. All the dealers we have spoken to say it will need a CLA as apparently the lube oil in those Ms tends to settle to the bottom if they are left unused. Said CLA starting at AUD $650. After all that, the eventual sale price likely to be $3000-$3500. The dealers were reluctant to get involved as they say they have to offer a warranty on all their sold cameras, and anything both (1) using film and (2) older than ten years is now a risk.
To sum all this up, oh well. Let the buyer beware.
Ending this with the sincere hope that your SL2 will avoid all these mishaps. There are some good ones out there.