If you don't take this job, will someone else be hired? What will their effectiveness be relative to yours? What alternative are you (and your hypothetical replacement) likely foregoing?

It seems to me like this is something that most people won't have good information on until after they've applied, made it through the interview process, and been offered the job, so this is not a reason to not apply.

My impression is that this particular job is standard secretarial work, with some personal assistant tasks (groceries? cleaning?) on the side.

Right, but it's worth pointing out that the historical impression is that a good secretary is a force multiplier.