Don't leave a hot water heater on with a chance that it will lose water! It will best case destroy itself, worst case become a steam bomb!
what about setting it to vacation mode?If you're home to monitor it, that's different. It'll be insulated and offer at least tepid water as long as the city water has pressure.
Shutting off a street spigot is a good start-- if a pipe bursts, it won't flood your house with a never ending supply of water.
You likely don't have a drain, so find the lowest point and open its faucet then open the other faucets so they can drain through. Follow up with some compressed air if you can find a way to rig it.
RV antifreeze, good luck finding it. Some is potable safe but most is not. It would be good for your toilet P-traps and sink traps but you'll have plenty of time to panic and put it in there if you're living there. Honestly cheap vodka might be the tonic to somehow force into your drinking water pipes, maybe with a funnel and hose from a 2nd story faucet. You just want it so that if ice forms, it won't burst your pipes. Alcohol can make it slushy and or lower the freezing point.