I had a Gitane touring bike with cottered cranks back in the day. It was a pretty nice bike, I ended up with a cheap Japanese cotterless crank on there. It's a big advantage from a maintenance perspective. It really depends on how much the bike has been ridden, and how cheap you can get the new crank for. A cottered crank that has been ridden to failure of the cotter pin is effectively junk. It can be put back together and run for a few months or longer, but it's really hard to fix them properly to stay fixed once a cotter pin goes.