Our neighbor built an elaborate ramp to his front door that started at the thin sidewalk between our houses. Because the narrow walk was not big enough for orienting a wheelchair, they literally sliced out a 3×3 chunk of our lawn and poured cement! We reported him and the city made him remove the cement but he didn’t have to replace the lawn. They also said that the ramp was illegal but because it was already up they wouldn’t make him take it down.
Make sure you get whatever info you need before he builds.