Personally I would only consider if very cheap. The battery packs are quite low capacity like 320Wh and because of this each cell is discharged at quite a high discharge rate so no surprise the battery pack is end of life, discharging cells at high levels shortens their life. However you have to factor in maybe both front and rear suspension need servicing and maybe the motor is getting close to needing replacement bearings or there could be a fault. I remember the huge Specialized recall for their Brose motors which were failing very quickly but that was the more powerful e-mountain bikes, I'm unsure of the reliability of the these models, I don't think they sell in such large quantities. The motors are lighter and low power but built much lighter too.
Many mid-drive proprietary e-bikes can become uneconomic to repair after only a few years where people decide they don't want to put huge money into them to keep them working but would rather replace. Also e-mountain bikes are aggressively used too and frames do fail too. So much to look at when considering such an ebike in my opinion. Do you have a local dealer who services and repairs such a model? Might be worth contacting them and asking about the cost of repair and servicing. I remember being in a shop and seeing a Bosch based ebike being returned to a customer after repair or servicing and the customer was paying about £700 for the repair or servicing in total. I didn't hear what the issue was, was it a motor repair or replacement or a new battery or was it a combination of things? It was only a road use step through model but a huge bill. As a general rule secondhand ebikes can be a dangerous purchase because you can get them when they require a lot of money put into them. For hub motor based ebikes often the battery becomes end of life when you would expect the hub motor to start being problematic perhaps need new nylon planetary gears and that is between 8,000 and 12,000 miles approx.
Mid-drive motors are a lot more complex and their failure rate is much less predictable but as a general rule they are less reliable than hub motors because of their complexity but this varies enormously and how they are used. As a general rule the motors for the very powerful e-mountain bikes which are often delivering 800-1000W of power despite their 250W rating tend to be less reliable so maybe there is hope this will be more reliable as much lower power.
The last thing I which is quite predictable for mid-drive is of course the drivetrain may need replacing like the cassette and chain, mid-drive puts all its power through the drivetrain so cassettes and chains wear fast so you would expect to be replacing them fairly regularly anyway and so fairly likely a secondhand ebike might need replacement parts there. However again as a lower power mid-drive motor but used off-road I guess this would be somewhere between a mid-drive motor designed for road use and a full on high power motor designed for off-road use.
