Does The Landlord Have The Right To Enter The Property Whenever They Want, And When There's No One Home. Or Should They Let Me Know In Advance?

My brother and his wife just brought a house, and im thinking about renting the house they were renting. My brother told me that the landlord just comes over whenever he wants. He doest'nt call before he comes , he just pops up. He even uses his key and comes in the house when theirs no one home. Is this legal.