Some years ago we moved into an old house, and we asked an electrician to come in and see what he thought of the wiring. Of course, you have to be sure that you can trust the spark, as he might tell you it needs done just to get the trade, but an electrician who is trustworthy should be able to give you an assessment of the state of your wiring.
Failing that is the rubber insulation cracking and falling away. Do the lights keep blowing ? Or flickering even ? Do you get a shock when touching the kettle or the washing machine ? Have you seen smoke billowing from the walls or floor ? Has your missus moved out and taken the kids ?
If it hasn't been checked for years, then have an EICR (electrical installation condition report). It only takes a few hours, but it's quite comprehensive.
You need one anyway every 10 years to be sure, so nothing wasted.
:-)
I'm no expert but if you want to rent out, don't you need certification of all sort of stuff ensuring safety ? I suspect you don't have much option but to pay an electrician to test and sign it safe.