What cheap thinkpad is best?

I don’t know - but would think what you intended to do with it might factor in.

Are you planning on playing games? What kinds?

Compiling code?

Just using cloud apps in browser?

It depends what you want in a laptop. I'd say the T480 is a great option because it's the last in the line without soldered RAM and has a fair amount of upgradability.

That said the T440P can do most of the same stuff but it's a little less powerful. Though I think you can upgrade the CPU to a degree.

There's other things as well like if you want to install Libreboot or sometimes people will sell the laptop and the dock together.

One rule of thumb is to be really sure it doesn't have a tn film screen. IPS at least and even those were really bad up until T490 etc. X1 series has better screens, but you cannot upgrade almost anything to those.

You want cheap ThinkPad, you best stop thinking about series.

Cheap ThinkPads (and most of second hand laptops) almost always come from decommissioned laptops after the company upgrades its fleet (Note that, decommission doesn't mean "not usable", in fact, it proves the laptops can stand a test of time)

Looking for a specific series of ThinkPad might spike up the price.

Just remember to change the batteries. You'll be Golden!

Whatever model you buy, avoid the newer L-series.

I think the best bet for quality/price it's T480 and T480s models

Saving this thread, I'm looking for the same.