I have heard that the new models are of very low quality. Rusting easily, engine issues, tank leaking, etc.
Should I buy a new one? Or buy a used model 2018 or before?
And how to check used YBR G for any issues before purchasing from someone?
Buying new one will be trouble free walk around at new bike & check for issues which you have asked & buy simple
YBR/GS/GD are bikes which lose their value very sharply - considering the same fact i bought a used YBR for myself in july2021 - it was a 2015 thai made model and i love every bit of it. it costed me around 110k which includes installation of brand new tyres (both), tuning/oil/filter/chain set and i daily commute on it for around 50km inside Khi. new one at that time was of over 195k. so i suggest you to look for a clean one which is single handedly used bike and buy from a genuine seller/owner. you will get a good bike and also save a good amount of money.