It's also important to remember if you're DIYing the project, that if your neighbour didn't use a generator interlock, your wiring may have enough power to make you need a trip to the hospital.
Seriously, speaking as someone who has worked as an electrician. Unless you're experienced, don't play with it.
> that if your neighbour didn't use a generator interlock, your wiring may have enough power to make you need a trip to the hospital.
If that happened you would know because your lights were on.
And what would actually happen is nothing, because the generator circuit breaker would blow from trying to power the entire neighborhood.
The only way this could happen is if you were right at the end of the feeder line, and managed to down a line such that only you and your neighbor were online - in which case enjoy the free power. (And then yell at your neighbor to fix it.)
Do things properly, sure, but don't over estimate the danger.
Your neighbor's house would still only have 120V on the lines, and they probably shouldn't be sticking knives in the electric socket just because the power is out. The real problem is that the pole transformer will step that power up to whatever higher voltage is normally feeding it and linemen may be in the middle of working on the downed lines.
It's literally only DIYable by someone who has enough experience that they could do it professionally. Installing your own generator interlock is no easy feat. Installing companion wiring for a generator, again, is no easy feat.
Easiest permanent DIY job would be to wire a dedicated outlet to your fridges and freezers and any important electrical equipment, and switch them to the generator outlet when you need it. No crossing circuits, no real problems.
If you have no electrical experience, deal with the extension cords.
Seriously, speaking as someone who has worked as an electrician. Unless you're experienced, don't play with it.