This is false. It's up to state law but generally speaking landlords can enter the premises without warning in case of an emergency, and can otherwise enter the premises for nearly any reason (inspection, routine maintenance, showing prospective clients, etc) with a 24 hour notice. Some states may increase that 24 hour notice to 48 hours, but yes a property owner can enter their property.
This is one of those cases where owners have rights too, and renters who want more rights should consider owning.
It's a common carve out in most states to allow immediate access for "emergency access", which is why everyone in the thread is discussing exactly that.
