What Intel Macbook should I get?

Their are a lot of dangers buying used Macs these days, especially the USB-C Apple laptops from 2016 - 2019/2020.

Make sure the laptop does not have a firmware password lock enabled by trying to Option-Boot the laptop. If a firmware password lock is enabled, then you will see a padlock on the screen. There is nothing you can do about it, so you should immediately return the laptop for a full refund. If a firmware lock is accidentally enabled after you own the laptop & you don't know the password (or the password does not work), then there is no way for you to have it removed since you won't have the necessary proof of purchase which Apple will accept.

Make sure the laptop is not being managed by a previous owner. This is harder to identify. Check the System Preferences to see if a "Profiles" item is listed. If any "Profiles" are listed return the laptop for a full refund because the previous owner did not properly prepare the Mac for sale and may still have control of it. If there are no "Profiles" listed, then make sure to perform a clean install of macOS. During initial setup make sure the laptop is connected to the Internet so that if the laptop is still being managed by a previous owner, the laptop will call home to Apple and hopefully alert you to the fact the laptop is being managed. However, this is not foolproof as there are times when you may not see any notifications until days or weeks later. If the laptop is being managed by a previous owner, then there is nothing you can do to prevent it.

With an older Mac, the chances of a worn out or failing battery are much more likely. Apple recently raised the prices for a battery replacement (assuming Apple still officially supports the laptop & has the part in stock). Battery repairs now easily cost $250+ US. Getting a third party battery replacement is unwise since the quality of third party Lithium batteries is extremely poor even when purchased from a respected vendor....besides it is a difficult repair where it is recommended an experienced professional perform the replacement. FYI, Apple currently only supports the 2017+ model laptops and the 2017 model will likely be marked as "Vintage" within the next year since the next major version of macOS will not be supported on a 2017 model. Avoid a third party Lithium Battery if at all possible.

Now we get to the really bad news regarding the hardware of the 2016+ USB-C models. They have a lot of known issues, with many known design flaws. The keyboards for the 2016-2019 models utilize a newer style of butterfly mechanism which has been nothing but trouble...so Apple went back to the more traditional scissor design with the later 2019+ models. Besides having known issues with the new key switches, the butterfly keyboards have virtually no tolerance for any type of debris...just about any small particles will interfere with the butterfly mechanism. Plus if you are touch typist, the feel of the butterfly keyboard is terrible.

The Displays for these laptops (especially the 2016 & 2017) models are known to have a higher rate of failure than any other models due to a poor design for the Display cable. This issue is not as bad for the 2018+ models, but they are still somewhat susceptible to the flaw.

The 2016 & 2017 models tend to have the USB-C ports wear out prematurely due to a poor design of the port. While the I/O Board is relatively inexpensive, it is a labor intensive repair to have them replaced.

continued....

The 2019 model (especially the 16") tend to have a much higher failure rate for the Logic Board. Personally I would avoid the 2019 models at all costs.

The 2018+ models utilize a T2 security chip which has introduced even more potential issues because I have encountered authentication issues with a number of our organization's 2018-2020 Intel Macs...some of which are due to bugs with the T2 implementation. When those issues are encountered, only a firmware "Restore" will get the laptop working again which will destroy all data on the internal SSD. There are lot more ways of losing access to your data on the Apple USB-C laptops 2016+ (especially with the 2018+ models), so make sure to always have frequent & regular backups. The firmware "Restore" requires access to another Mac running macOS 12.4+ (at least for now...Apple has been increasing this OS requirement for the host...my guess it will be 13.x by next year).

Keep in mind most Apple USB-C laptops have the SSD & memory integrated onto the Logic Board which means there is no way to upgrade these components later. It also means that there is no way to recover data from these laptops if anything goes wrong with the hardware (or with the ability to authenticate with a 2018+ model). Make sure you always have frequent backups.

Personally I would check the health of the SSD to make sure the SSD is not wearing out. Unfortunately most SSDs do not fail due to old age or from excessive wear. Most SSD failures I have encountered are due to the SSD's controller failing which can occur quite suddenly with little to no warning. Recently, however, I have been finding a small number of our organization's Apple older laptops showing worn out SSDs which is starting to concern me, but I don't have enough failures or details to understand what is happening yet. You can check the health of an SSD by using DriveDx (trial period available). Unfortunately the SSD health information must be manually inspected & interpreted. The Spare percentage (must consider it with the Threshold), Used percentage, Written amount, and whether there are any "Media & data Integrity" errors. Keep in mind if the amount written is approaching 100's of TBs (TerraBytes), then that is a bad sign since some SSDs are only made to support 300TB - 500TB for their lifetime, although it may be possible to write a lot more data to them...hard to say when the SSD may fail if that much data has already been written. Unfortunately the health information provided by these SSDs is quite limited so it is very hard to really assess their health properly.

Unfortunately the 2016-2019 USB-C laptops have been the most troublesome models in a long time even when brand new so it makes recommending a used Mac very difficult. I still haven't worked enough with the 2020+ Apple Silicon models to know how well they are holding up yet. So far I haven't seen anything quite as concerning as the 2016-2019 Intel models.

Be very careful purchasing a used Mac from unknown sources. Your best option is to purchase a refurbished laptop directly from Apple. Next best option is from a well known vendor with a great reputation...like OWC. Of course these more reputable vendors will likely charge a premium for a used computer.

Good luck.