Chest freezer for fermenting

I am looking to buy a 7 or 5 cu ft. Freezer to control fermenting temperatures. The guy at the appliance store told me that if I unplug the freezer when not in use it will rust out. He said the lines are steel not copper. Is this true? What do you brewers that use chest freezers for fermentation do? Let it run or unplug them?
Thank you.

When used as a freezer, the unit reaches temp and shuts off on it’s own for 2-3 hours the lines are going to rust?

Find a new appliance store.

The freezer can rust out in the seams. Applying some caulking will prevent this.

If I’m not using it as a ferm chamber then I’m using it as a lagering chamber. So, it never gets unplugged.