Short answer…Used (with one exception).
Long answer...There are two basic types of pianos: acoustic and electronic (digital) and lots of models of each. Both are often for sale on Craigslist. The hybrid, as the name suggests is a combination of both and is the only one I recommend buying new.
Digital Pianos
Most digital pianos can’t really duplicate the sound or experience of an acoustic piano, but they have lots of good features and are often the perfect selection for beginner to intermediate students.
They don’t need to be tuned (so you’ll save $100-$200 a pop!).
Most are lightweight enough to move from room to room.
They often have a headphone jack so you can practice to your heart’s content without driving your neighbors crazy.
Most have lots of options such as “voices”, like string sounds or brass sounds, drum beats, and more. Some have built in metronomes and some allow you to record what you play, a feature I particularly like.
The best digital pianos have great piano sound and a full (88 key) weighted keyboard. If you can, go for this option because the weighted keyboards are best for developing finger strength and technique. Most students will be happy with this alternative for at least 5 years, perhaps many more.
The next best digital pianos have touch sensitivity and 61 – 76 keys. What you are looking for here is how many C notes are included – you’ll want at least six. Some 61 key keyboards have as many C’s as a 76 key keyboard. It could save you a few bucks to go with the lesser, and these will do in a pinch. They may be sufficient for up to three years.
The worst keyboards have no touch sensitivity, really poor sound quality and are little more than sophisticated toys. Many have lots of bells and whistles -- very entertaining but not necessarily helpful. These keyboards might do the trick for 1 to 3 months of lessons but will end up frustrating the student. Avoid these at any price except If one comes your way for free. If so, and you have nothing else for your beginner, grab it while you look around for something better. This at least buys you some time.
Casio and Yamaha both have decent affordable digital pianos. There are websites that compare all kinds if you want to do the research.
Acoustic Piano
Acoustic pianos have the best keyboard action and often superior sound to digital pianos. They can last a lifetime and beyond and they are often offered free for the taking on Craigslist. But…
They are considerably heavier than their digital counterparts and they need to be tuned at least once a year. They prefer an even humidity. (I have both a humidifier for winter and a dehumidifier for summer). Sometimes they need additional adjustments that can only be provided by a professional piano technician. And they don’t have headphone capability so practice sessions will be heard, which can be difficult for apartment.
The very best are so beautifully constructed that playing a single note can bring a tear to your eye, but these are rare and often beyond most people’s price range. That said, there are many decent acoustic spinet, studio, upright and even baby grand pianos available used both on Craigslist and at piano stores.
Baldwin, Yamaha, and Kawaii are usually reliable (as are others) but if purchasing privately, it is best to have the instrument checked out by a piano technician before handing over your cash. They can let you know quickly if the instrument needs repairs and if it is worth the investment. Also, there is a blue book of pianos to help you figure things out. My top recommendation is a Studio Piano which will serve you faithfully for many years.
Hybrid Pianos
Until recently, no digital piano could truly match the feel of a real piano, essential for any serious pianist. That has changed as the most recent models offer all the benefits of an electronic piano, like portability and ability to be used with headphones, plus sound modules that duplicate some of the best pianos ever built combined with real grand piano keyboard action. You now have an instrument worthy of a concert pianist’s attention. That is exactly why piano makers like Kawai and Yamaha developed the Hybrid piano.
There are relatively few on the market and fewer still available used and you have to be extremely hybrid-savvy. There have been vast improvements in the short time hybrids have been on the market and it is well worth the money to have the latest available technology, not to mention a warranty just in case…
Sound through the headphones is amazing, but cannot really compete with the sound experience of an acoustic piano without hooking it up to external speakers.
I am the happy owner of both an acoustic and hybrid piano but in my opinion, hybrids seem unnecessarily expensive for the needs of a beginner student. They may be the future but there’s still lots of room for improvement. Maybe by the time your beginner is ready for a hybrid it will be all it hopes to be -- the answer to every aspiring and accomplished pianist.