It's reasonable to ask them to start it and run it over a patch of grass to make sure it works, right?
I've never bought anything like this secondhand before, and I want to make sure it's not weird of me to ask that.
Anything else I should be aware of when looking at a used mower?
Re: Buying a lawnmower off CL
Does the listing say what kind of mower it is? You might be able to research the model online and know what kinds of features it has or if there are common complaints about it, which might help you generate some questions to ask or have them demonstrate for you.
We sold our couch on CL-the buyers came over and sat on the different cushions for about 10 minutes and pored over the fabric to make sure there weren't tears, tried all the zippers, etc. I didn't bat an eye. CL is buyer beware, so I'd rather be weird about these things than get a lemon.