Once you have made the decision to take up the piano, or any musical instrument for that matter, the first thing you will need is an instrument (preferably of your own) on which to practise. Becoming proficient at any skill requires an investment of time and dedication, and much repetition of each new technical point until it becomes second nature. So before starting to take lessons, consider carefully the type and quality of equipment you are going to use.
If the piano is your chosen instrument, try to get hold of a piano - whether it be acoustic or digital - rather than an electronic keyboard, which you'll soon discover, feels and sounds very different. The techniques you will be learning in piano lessons will be difficult to achieve fully on the keyboard, and cause problems with finger control and tone when coming back to playing a piano.
You may find this Noteworthy blog post on Buying a Piano helpful.
On the other hand, a keyboard has features that a piano doesn't, and can be fun to learn as an instrument in it's own right!
If you are unsure whether to learn piano or keyboard, I would suggest that the piano is likely to be more rewarding in the long-run. In any case, learning the piano will give you the skills to play almost any kind of keyboard instrument, whereas learning the keyboard alone will be limiting.
Before buying an instrument, it is wise to consult an expert to ensure a suitable choice for your individual needs. Most teachers will provide free advice as part of their service, but even if you have to pay for consultation, it may save you expense in the long run, as well as the risk of frustration and embarrassment of getting something inadequate.