One way to interpret this is that you're going to potentially buy the place first with cash as is, then evaluate whether the well and septic work afterwards - knowing they they may or may not work, and willing to write them off as necessary (but also willing to be pleasantly surprised).
If that's the case, I'd still try to get any records that exist on the wells and septic - but don't be surprised if you don't find any.
Once you get power to the place, you could try just turning on the breaker to the well, and see what happens. Think of it as a smoke test. Connect a hose to it, and shut off the rest of the house, if it's possible to do so (otherwise you'll be testing two things - the well, and the integrity of the house's plumbing - at the same time). If it doesn't work, then you are on your way to finding out what you need to fix or replace. If it does, then the next step is to evaluate the quantity (Well recovery gpm, pump gpm, reserve capacity of well), and quality (send sample to lab) of water produced by the well.
I've actually done this once, with a well that hadn't been used for about 5 years. It was a submersible pump, and started up just fine. The well produced good quantities of excellent water that tested well
I think the septic would be harder for you to evaluate, as a failure may not be immediately apparent. The biggest red flag to me is that it is a mound system, which indicates that the soil on the property is poorly drained (if that matters to you). On the plus side, whoever put it in spent some money, and at least attempted to solve the poor soil drainage problem the right way.