I don't know anything about this bike or it's wheel size, condition, whether the rim is small and rigid or has more than enough spokes, etc.

The issue to me then is whether it is safe to jump on any used bike and ride, just because it seems ok.

I've known riders to just take some used road bike out for high-mileage, high-speed riding without ever even inspecting the rim tape, to see if perhaps a sudden air loss was imminent.

Any used bike should be thoroughly inspected by a qualified person before being put into service, as should any new department-store bike.
Such an inspection checks everything, from spoke tension to a close visual inspection of every inch of the chain, and every nut and bolt on the bike.

In either case, it is much of a gamble as to whether one of many possible failures is likely. Having a tire's tread peel off, having a chain break, or having a caliper fall apart are not good things, and I've seen longer-term neglect result in a fork steerer left with no threads because the headset locknut wasn't kept tight.

This bike's back wheel might be the least of the rider's concerns.