Additional notes to Bruce's answer.
The problem with learning without a teacher is understanding whether your posture, finger technique and interpretation of the music score is correct.
As an older starter I am mindful of acquiring a physical injury as I do not want to stop learning to recover. Recently, I have used Murray MacLaughlin's book on The Foundations of Piano Technique, particularly the early chapters on finger independence, thumb and the importance of removing tension while keeping the knuckles to fingertips firm/strong. I have also watched some 10 year-old YouTube videos from the Edna Golandsky Institute who teach the Dorothy Taubman technique which aims to avoid injury by removing stretches and awkward movements (e.g. Thumb technique). They overlap but don't agree entirely with each other (e.g. Is the Thumb under technique - good or bad?). They both seem to draw on the Alexander Technique (which I have not studied) to an extent.
Depending on the repertoire you like to play, a teacher will provide insight into the shortcuts in writing down of music notation, the rhythmic emphasis that were made. This particularly applies to the Baroque period (JS Bach, Handel, et al) - played as written can sound rather dull, but with the right articulations (nothing clever) a piece can come to life. Try to find good sources on performing a piece that help you interpret the music scores correctly (i.e. as the composer would have expected the music to sound).