I lived aboard last winter. I kept a small space eater on all the time to keep it warm inside the cabin. I kept all seacocks closed except the cockpit drains. I kept fresh water for cooking and drinking, but showered in the marinas facility.
The only fresh water lines
that I ever had problems with where the hot water lines
that run through my engine compartment. It got colder in there with no warm air flowing in. Those lines
stopped flowing a few times, but never burst. To correct it I just turned the water heater on for a little while and it would flow again.
Depending on if your water lines
are routed through areas that will stay warm from your cabin heat or not, you may have problems with them freezing.
When I used any water (cooking, cleaning, teeth brushing, etc) i would open the sink drain seacock, let it drain, the close it back off immediately so i didn't forget it.
I wintertized the engine, that's a must do. It gets cold in the engine room. Unless you install a small heater in there, and even if you do, winterize the engine. If the engine freezes it'll be big bucks to fix.