What to watch out for?
Watch out for poorly trained and inexperienced teachers. Do some research and book trial lessons with at least 2 teachers to see what they have to offer.
Professional teachers should be suitably qualified with a degree or diploma in music, piano performance, or piano pedagogy from a respected institution. They should be teaching full-time and not on the side to complement another career.
A good teacher should also be a member of a professional body such as the ISM (Incorporated Society of Musicians) or EPTA (European Piano Teachers Association).