gonna depend on how much heat your lights put out, size of the greenhouse and outdoor weather, but its definitely doable to have supplemental lighting in a greenhouse if you plan correctly
Disagree, if you are legal you aren't required to tell anyone. The downside of telling neighbors is that you increase the odds of getting ripped off from word of mouth. If you are NOT LEGAL, don't confess to committing a crime. No real advantage of telling anyone anything, IMO