Learning the piano requires practice at home so an instrument is definitely required to start lessons. I recommend starting out with a keyboard, making sure you also get a stand and stool.
Keyboards are not only more affordable but also have lighter keys than a digital piano which is perfect for gently developing finger strength and technique. Acoustic and digital pianos have heavier keys which can cause tension while the fingers are weak and underdeveloped. The keyboard will allow the fingers to develop naturally with a relaxed style. Finally, a keyboard is a cost-effective way of giving lessons a go without having to make a huge investment in an expensive instrument.
Check out Facebook Market Place / Gumtree first and if nothing looks suitable then you should find something at Amazon / Wish / Catch / My Deal.
LEARNT FOR 6+ MONTHS
After learning for around 6 months (adult student) or 12 months (child student) it is time to upgrade from a keyboard. Keyboards do the job in the beginning but from a certain point in the piano lesson journey we need weighted keys and sensitive touch capabilities found in digital and acoustic pianos. Keyboards won't help the student develop the techniques and skills required to grow further. Upgrading your instrument will be so beneficial for the student's musical development and will add to their enjoyment level as it is so much more beautiful to play on.
I highly recommend buying from Australian Piano Warehouse as they a great to deal with and they will price match. They are very helpful and willing to do what they can to make sure your instrument does what it is meant to do. I have associated with them for many years and I am very confident in my recommendation. Tell them you know me and they will look after you. When you buy new you have the confidence that if something goes wrong, you are covered. Buying secondhand is a risky game. You don’t know the history of the machine and if something goes wrong you don’t have Australian Piano Warehouse to help you out. If you do decide to buy a secondhand digital piano anyway, make sure it is only a max of 2 years old and get as much history on it as you can so you don’t buy a dud.
Roland is the only brand you should consider when it comes to digital pianos. They have the best touch response and velocity sensitivity by far on the market. Casio is far inferior in quality so I would suggest staying away from that brand. Yamaha is good (they excel in acoustic pianos) but you need to spend at least $4000 to get anywhere close to the realistic piano feel, though Roland still trumps them in quality as they specialise in digital pianos.
Having done the research for you I highly recommend the Roland F-701. It is the entry-level to Roland's realistic piano feel range.
Info on the instrument - https://www.roland.com/au/products/f701/
Where to buy - https://www.australianpianowarehouse.com.au/product/roland-f701cb/
If you would prefer to upgrade to an acoustic piano, please know that it is a much more expensive option. Cheap pianos you find on Gumtree are not worth your time. Pianos need constant maintenance to keep them in good working condition so you will find that cheap pianos are in terrible working condition and will actually cost a lot to fix. To buy a good quality second-hand acoustic piano you are looking at spending at least $5000.
Yamaha is the only brand you should consider. They have the most beautiful sound and the highest quality made pianos. The piano needs to be at least 120cm tall, anything less and it isn’t worth your time and money. (Kawai is also a great brand but only if they are made before a certain year).
If you want to go down this path, let me know and I will connect you to my trusted piano tuner who can line you up with a good quality second-hand piano.