The P-71 is the same as the P-45 but the P-71 was sold through Amazon that's the only difference. I didn't like it, seemed underwhelming sound wise and the upper register was strangely too low in volume. The P-125 is a better keyboard. Generally I prefer Kawai as they do the best job sampling every key to avoid the strange clash in tone from key to key that happens when other makers, Yamaha and Roland included, use less samples and digitally change the frequency of the note to sound on neighboring keys which causes brassiness on some notes. You might find a ES110 or ES120 used or ES60 can be had new for not a lot more. More on reddit.com

Plug it in and play Every. Single. Key. Check for scratches everywhere. Make sure the pedal functions properly. I don’t know what ‘voices’ might be included but test all of them. Test all of the buttons. If it has ‘weighted’ keys make sure you press each key both softly and firmly to make sure there is a difference in volume. Make sure there isn’t a lot of gunk in between the keys. But ultimately don’t look a gift horse in the mouth. If it works appropriately then a scratch or two won’t be the end of the world. More on reddit.com

You mentioned that you want to buy Yamaha Keyboard that you won't need to change in the future, correct? If that what you wanted. I recommend you to buy Yamaha P-515. This Yamaha will serve you well for 10 years to come. The key action is great, piano sound outstanding, speaker sound is pretty loud. It has jack output, MIDI connection, Bluetooth, Metronome, music/band and other sounds. A few of my students bought this Keyboard and feel satisfied even after 2 years. If you are adult and want to learn yourself, I recommended piano book Alfred for Adult. If you really serious want to practice, you should prepare to spend at least one hour for the first 2 months (24 days). That's 24 hours/month. If you want more that's great. That's even better. After that, you can keep increasing the hours of practice. Most intermediate practice about 4 hours every day. Advance practice 8 hours/day. Ling ling practice 40 hours/day. That's just a side joke. Anytime. DM me if you need more help. Good luck in your music journey. More on reddit.com

They will give you a small amount for it- I’d guess around $125 More on reddit.com