Less than 20k ideally
I don’t want to spoil your dream or teach you to suck eggs, but do bear in mind that the Gen1 FZS1000 were only made from 2001 - 2005. Therefore they will all be between 16 - 20yrs old. You’re not going to have a very big choice available to you if you want only those below 20k, an average annual mileage between 1000 - 1250? They are out there, but I wouldn’t have thought that they’d be plentiful?
There is a school of thought that says that a bike that has plenty of miles under its belt after fifteen years BUT, has been well maintained by a few long term owner, might be a better buy than one that has done minimal mileage over the same period / changed hands plenty of times / been serviced on mileage rather than time.
By way of an example, I’ve owned mine for about nine years now. It’s still only got about 26- 27k on it, of which I’ve probably
done 8k. But.............it normally gets an oil and filter annually, along with the exup valve getting a service. Brake fluid every two or three years etc etc The Gen1, if well maintained, is good for some big mileages.
Just my thoughts. Good luck with your search.