They are a reputable business as far as I know, and are in the business for a number of years. They act as agents for holiday home owners, getting clients and handling changeovers etc. They have a strong presence on internet searches. I have a holiday home in Nice but have no connection with them. I'm sure they will give you email addresses of past visitors to reassure you. Enjoy Nice, September is a great time to visit, less crowded and generally good weather.