Ask in advance about who's responsible for hardware health monitoring, recommended tools for that, and how they handle hardware failures. Bonus - how they respond to such questions may separate the good providers of private rent-a-servers from the not-so-good ones.

Who faces the immediate consequences of failed hardware --- that's who needs to monitor it.

Disk monitoring isn't too hard though. For hard drives, run smartctl once an hour, alert when reallocated or pending sectors grows quickly or hits 100. For SSDs, cross your fingers; in my experience with a few thousand, they tend to work great until they disappear from the bus, never to be seen again. Have a data recovery plan that doesn't involve storage of the data onto the same model devices with very similar power on hours --- power on hour correlated firmware errors are real.

Not if you build a cluster with disposable nodes.