The more it looks like a "work in progress", the more that it will attract vandals and thieves:
If you have good insurance; is the most important thing.
Do not leave tools at night.
Do not leave new materials, like light fixtures, etc.
Leave a light or two on each night; never the same one.
Come by on an irregular schedule; don't be predictable.
Leave a radio on, loud enough to hear from the outside.
Hire a guard dog.