When buying anything, one appears to have just two choices -
1/ Brand spanking new, box fresh with a guarantee from a (hopefully) trusted source. With an Apple machine, that will inevitably be Apple, so trust is a given.
2/ Secondhand - pre-owned, pre-loved, or any number of dressed up terms to describe 'used'. The problem is one of trust and the relative values attributed to those terms. Who on earth are you buying from? Is it used or abused? Is a complete stranger's definition of 'love' similar to yours? Is you new-old Mac ever going to show up (in one piece)?
As a seasoned eBay warrior, I've bought many things on the used market, and though my experiences are generally good, my disappointment/ not-as-described/ filthy/ not showing up quota lies at around 5% of purchases. I wouldn't want a computer in that 5%.
The third way
Yes, there is a third option, and that's buying a refurbished machine. Sure, it's still used, but a it is way safer for several very good reasons.
The most important overall point about buying a refurbished Mac from an established reputable company is that it isn't merely passed on to you blind from an individual. It's refurbished. So what does that mean?
The first thing that a refurbisher will do will be to give it a damn good clean. As I type this, I shamefully note the state of my Mac Pro keyboard. Who wants somebody else's....erm....finger cheese? Also - have you ever opened up your computer to take a peek inside? The picture above is really no exaggeration - any computer is a dust magnet. Dings, coffee stains, scratches, dusty cameras, blocked ports.
Your new refurbished MacBook Pro will have been thoroughly cleaned, inside and out. Any dents will have either been removed or clearly described in advance. No nasty surprises.
A refurbished machine will also be thoroughly tested inside and out. No flaky screen, dead battery, semi-functioning trackpad or dying memory. All reputable refurb sellers carry stocks of spare parts, so anything dodgy will have been replaced. They'll also securely wipe any data and re-install an OS of your choice. You'd be surprised what people leave on their machines...
Great as Apple machines are, there have been recalls of certain machines over the years - it's unusual, but does happen. Refurb companies know their Macs inside out. They simply won't sell a machine that's been recalled without having Apple carry out the necessary repairs. They don't want to burn your house down.
Send it back
Let's make a distinction here:- by 'refurbished', I'm recommending established companies that specialise in Macs - not some guy in Wigan advertising on eBay (nothing wrong with Wigan or eBay, but...).
Most importantly, any good refurb company will give you a 12 months no quibble guarantee - that's exactly the same as you get from Apple for a new machine.
Peace. Of. Mind.