Generally, Honda mowers seem to perform very well for a reasonable service life and then become both difficult and expensive to repair. That doesn't tell us what is wrong with this one, however.
You could consider buying the mower, finding the cost of repairing the self propulsion system, and if it is too much, using it as a push mower. The heart of any small mower like that is the engine, and it sounds as if the engine is in good shape. I suggest you don't buy it unless the engine is good - it's a Honda, and repairing it is likely to be difficult and expensive.
