You cannot protect people against themselves, better provide the last pieces and help him out. An electrician ought to check out the house once a year though, in particular with old installations (or an enthusiastic amateur electrician living there!).
I've done a lot of work and has never had an accident or injury nor damage to my house. I always carry a tiny black pen-sized screwdriver that detects voltage to ground and any fields extending out (usually up to 10 cm from a live 230V wire). This little thing cost me around 3 euro and can detect/locate broken or shorted wires such as an extension cord shorted out somewhere. Every amateur ought to own one(*), it detects extremely lov AC/DC voltages even below 12 V if used correctly. It's also nice to detect a blown fuse in 10 secs instead of checking a dozen fuses, in fact it has so many uses(espec. if you have a small cell phone charger handy to generate a little current) that I can hardly think of them all but first and foremost think *safety* is the one.
(*) No I don't know where to buy them, maybe a hardware store, found mine buried in the the mixed items discount shelf (cheap import from asia, mine was).