How will you communicate with each other?  Do ham radios work without electricity?

With Ham Radio.

I see you've prepared a snarky counter-question in advance, but here's my response to your snark: you obviously know little to nothing about ham radio.

Unless we're talking about a supernatural outage (a la the Three Days of Darkness), solar panels, batteries, and generators will work just fine.

Ham Radios operate on 12V DC like a car battery or marine deep cycle battery would provide. Even when you're operating at home on-the-grid, you use a separate "power supply" which takes your 120V A/C mains power and turns it into 12V DC -- and that is plugged into your radio. But radios all run off 12V DC natively.

Hams routinely go to parks, mountaintops, and other summits for "portable" operations. Twice a year countless hams (not just those super "into" portable operating) go to parks and set up for Summer Field Day and then again for Winter Field Day. Not to mention "mobile" radios found in cars, which are quite numerous. You will need solar panels or generators to recharge those batteries, yes, but most hams have this. Especially those with an inclination towards preparedness, emergency comms, and/or portable operation. There are hundreds of sub-hobbies within the VERY BROAD Ham Radio hobby.

Hams tend to have an above-average number of batteries in their possession, of all types and sizes, around the shack. LiPo, NiMH, Lithium Iron Phosphate, sealed AGM, Lead-acid, etc. Both household sizes like AA and 9V (to power small equipment) but also various other battery packs and "car battery" size batteries -- ranging from 5 lbs up to 100 lbs.  And, of course, they have various ways to charge them. Hams really like solar panels.

Morse Code receiving/sending takes about 1/10th the power to make it the same distance -- so it will be very useful in a grid-down or collapse scenario. So it helps to know and practice the Code now. It's also about 10-50X easier to build your own radio from parts, if you just want to send morse code vs. sending and receiving voice.

We have sanitation covered too. We already burn our trash, and with our acreage we have plenty of places to put food waste to compost. As for toilets, we can continue to use the toilets we have now, since we have a septic system -- NOT THE ELECTRICITY-USING AEROBIC KIND -- for both our buildings. So we just need to bring in rainwater, greywater, etc. and manually refill the toilet tanks, and they will flush -- right into the septic tanks like usual. 100% sanitary.

I wish we were as well-prepared in other areas, as we are in Sanitation and Comms :)

I always hope that being in the top 5% prepared will be enough. If that is the case, then we are set. But we certainly have plenty of room for improvement, as do most people. I don't spend 100% of my time on preparedness. Especially not lately. It's very much a part time thing now, as time allows. Mostly just getting my property in order, easier to maintain (=more time for other things), etc.

Ham Radios operate on 12V DC like a car battery or marine deep cycle battery would provide. Even when you're operating at home on-the-grid, you use a separate "power supply" which takes your 120V A/C mains power and turns it into 12V DC -- and that is plugged into your radio. But radios all run off 12V DC natively.

Some of our homes are 12/24VDC native, everything plugged into the inverter the exception to the rule 

How Long Can You Survive Off Grid?

Depends where one lives. If one lives in an apartment in the city in a cold climate, I think they'd freeze to death, or get eaten by someone with heat. If one lives in the a warm climate they'd be better off. If one lives in a rural environment with a warm climate they could do well.

Some of our homes are 12/24VDC native, everything plugged into the inverter the exception to the rule

That is one advantage of living in an RV -- but let's face it, there plenty of downsides... storage space for one, strong shelter for another. And how do you heat your home in a grid down scenario?

Also, do you have land (acreage) to park it on, or do you just rent from someone? Issues like security, sewage, water supply, etc. could be a problem.

Now we have rainwater tanks with lovely clear water.

And we have discovered a spring on our block.

It's really good that you have a spring on your block. May I ask about how you collect rainwater? I assume that you collect from your home's roof. 

That is one advantage of living in an RV -- but let's face it, there plenty of downsides... storage space for one, strong shelter for another. And how do you heat your home in a grid down scenario?

Also, do you have land (acreage) to park it on, or do you just rent from someone? Issues like security, sewage, water supply, etc. could be a problem.

My house is primarily DC appliances (if you can call them that lol... Don't have anything with that heavy of a draw) with some AC (my bank is LiFePo4 since you probably are interested in details like that) stuff that my wife uses. I have some electronics gear that I use with AC as well and there's no cleaner power than inverter power so thankfully I don't have to worry as much about my vintage electronics. I'm ten miles from nearest town of ~40 people, stream on property (house water is collected from roof into a cistern), it's treed so I can heat my house, no municipal utilities or anything. Elon Musk provides me internet. Life is good for now but that can change. Security is always the biggest issue. Anything can be overcome with numbers, even though the terrain is defensible and the neighbors are likeminded (unfortunately not Catholic).

We only relocated in January. We have always collected rainwater and always off the house roof.

In April we purchased a 3000 litre tank, and last week a 1150 litre tank which collects off the roof of the caravan shelter* which we also built this year.

*spare accomodation should family visit (unlikely) or should someone be in need (likely).

Very nice. I'm trying to upgrade my water storage as well. Water is so abundant until it isn't (seems so obvious but you never really have all the water you could possibly want). My problem is my stream is year round but not always accessible as I'd like, so for me a cistern upgrade would be good peace of mind in case I have a large group of people over or something :)