Unless you've just fitted brand new tyres onto your car's wheels, you're already driving on 'part worns' anyway. I've bought plenty of them and never had a problem.
A lot of the part worn tyres come from Germany where tyres are required to be changed in pairs. If one tyre has a puncture which cannot be repaired, both tyres on that axle will be renewed, even if they have only done a few miles.
Yes. I have bought these tyres but try to go for named brands like Pirrelli, Goodyear etc.
I see it as saving me money and being more ecologically sound by recycling these tyres.
In many countries there is a requirement for all tyres on any axle to be the very same brand, pattern, etc. (different axles my have different sets). Because availability varies, it is not uncommon for one tyre on a car to have to be changed when the other on that axle is unserviceable (for whatever reason). I have bought used tyres in the past and would do so again.
Is your life worth it? the tyres could have been kerbed causing damage to the casingere could be damage that the sellers knows about and you are unaware of not chance it Bazile.