Buying a new(er) phone every year or so means you can sell or trade-in your old phone.
You can google "where to sell cellphone" to get lots of info - but note the date of what you're reading as things change quite a bit over time.
You should wipe your data from the old phone - after you make sure everything you need off it is put on the new phone.
http://www.hard-reset.com will tell you how to do it for most any mobile device.
The last 3 (maybe 4) phones I bought were 'refurbished'. It saves me money and gives me 90 days to exchange it or get a refund if something doesn't work.
I research (google search) "best budget cell phone" and find the ones that have recently been 'replaced' by a newer model/version - this takes the price down another notch. Once I narrow it down to 2 or 3 phones, I search/read reviews of those models to pick the one that will be best for me.
My daughter use to sell cell phones and use to buy a different used phone every 6 mos or so. She said she's "only had a problem a couple of times".
Note that the newer the phone, the more likely it can be upgraded to new version(s) of Android. Because of this, I think you shouldn't buy the cheapest phone you can find.
Then, I google "refurbished {the model}". You may get multiple hits for amazon - it's because there's a lot of sellers on amazon. I always note the sellers ratings.
Oh, you have to pick your carrier (cell service Co.) before you pick a phone as not all phones work on all carriers (for now, I've read that's changing). The carrier has to allow 'bring your own device' (BYOD), which means use a phone you didn't buy from them. Part of your phone research is confirming it works on your chosen carrier.
I JUST bought a Motorola Moto G4 (not + or play). I've started doing some side gigs and I'm finding some of them are app (and cell data) based. It's my first 4G phone. It is WAY faster and sharper than my current Moto G (1st or 2nd gen.).
I've been on PagePlus cell service for years. It uses the Verizon network, which is important to me because it has the best coverage in rural areas - where it can be hard to find WiFi. It's been $12/mo - with very little (3G) data.
But I learned on here (Thx I.P. Daley) that it's recently been sold to a Co. with poor customer service, so I'm getting Selectel for the new phone. They are also on the Verizon network. $30/mo gives 1.5K minutes, unlimited texts and 1Gb of 4G data. $40 is unlimited talk and text w/ 2 Gb data.
Note that phones for Verizon pre-paid do not work on PagePlus or Selectel.
