Never heard of a Carftman anything.

Does it have good compression? Does it run? Do the blades engage and cut? Can you get the parts you need for maintenance?

Yes to all questions husband has changed oil filter lubed it all up and is getting new blades

Seems a bit high unless $400 includes the mower and all the repairs. The new battery, blades, tubes is at least another hundred +. There’s a guy that I drive by on my way to work that fixes and sells them and I see riders generally priced at about $300 up to $1k depending on age and shape. This one would be about 20 years old, but of course condition and how it was treated counts too.