Mortgage: Second/Vacation home -> Rental

[Sunny Er]

Hi,

If I buy a home with a secondary/Vacation home mortgage how much time do I have to live in it before I can rent it out? Also:

1) What does it mean to live in a house: having utilities in my name? Not claiming any rental income or depreciation on the tax returns?.. or something else?

2) Can I move in and rent out a room immediately just to have company, and also show that on my tax returns? I am single. Will I be adhering to the second/vacation home mortgage requirements?

3) What bad things can happen if I turn it into a rental "too soon" and what is the probability of those "bad things" happening?

Why: I can WFH for at least 6 months, so thinking to move from the bay area, CA to live close to the mountains for some time.

Thanks!