Piano teachers oftentimes receive this question from new potential students: "I don't have a piano or keyboard. Can I still start taking lessons?". Well, the answer is unfortunately, NO. It's because the most important thing about learning how to play piano is to practice at home during the week (if you are going to take weekly lessons). If you have a very small budget and also you are not sure if this is something that you really want to continue doing, then, if I were you, I would get an inexpensive keyboard. And if or when you are sure that you want to continue with lessons for a long time you can upgrade from that keyboard to either a digital piano or acoustic piano.