I don't know what to avoid but I can make a recommendation. The institutional Dell laptops are pretty solid. I bought a used D630 with win7, upgraded to win10 and a SSD and it's been my daily use PC for about 6 years(so far). Total cost-less than $200. I bought a newer Dell E6420 as a backup but have not used it yet except to keep it updated.

__________________
Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT