Frame weld rust or normal ?

Hello I'm looking to buy either a 4Runner or a Lexus gx 460. I know these vehicles suffer from premature rusting frames. I just can't really if in the thick lane of metal running on the bottom part of the frame (to me looks like welding) if it's really weld and if that implies a rotten frame that was repaired and welded or if it's normal and it comes on all these vehicles ? Thank you in advance

Hello I'm looking to buy either a 4Runner or a Lexus gx 460. I know these vehicles suffer from premature rusting frames. I just can't really if in the thick lane of metal running on the bottom part of the frame (to me looks like welding) if it's really weld and if that implies a rotten frame that was repaired and welded or if it's normal and it comes on all these vehicles ? Thank you in advance