If you’re serious about wanting to learn to play piano, you should sign up for lessons. Piano lessons aren’t just for kids. Adults take lessons all the time. In fact, many accomplished players take piano lessons in a different style than they’re used to. Even piano teachers can sign up for lessons to expand their horizons a little bit. Someone who teaches classical piano may sign-up for lessons in improvisational jazz, for instance.
So it’s nothing out of the ordinary for an adult who’s never played or even for teachers to sign up for serious piano lessons. You can learn to play piano on your own if you like, but you will get the valuable feedback from an instructor. If you learn bad habits doing it on your own, those are harder to break later on. But if you start with the teacher and then branch off to learn on your own at least you will have a good foundation to work from. And taking at least a few lessons in the beginning can make sure that you use the proper technique and the correct fingers.
If you’re strapped for cash and can’t afford a few lessons, then you might want to invest in some sort of DVD or video course. This takes money, too. But you only have to pay for it once rather than pay for an ongoing weekly lesson. And it’s a good way to get the basics and be able to learn them at your own pace rather than having to go once a week for a lesson.
If you don’t own a piano you can still learn to play piano. You can use some type of a cheap electronic keyboard but it won’t be the same because the key touch is vastly different from a real piano keyboard. Still, it’s a good way to learn the notes and the keys.