So long as an employer has approved you to go remote from an office, the cost of you coming into an office now and then is on them. And, frankly, if you just move without telling them, you're potentially committing tax fraud. Of course, it's possible to reach informal agreements--let me go remote and I'll pay for coming in now and then. Though, personally, I'd hesitate to do so because that agreement might not last beyond getting a new manager.