I see quite some rough patches on structural area's; that's good and bad: 'Good' as in it saved the car from scrapping, and apart from the obvious welding marks, there is little rust to be seen. Let's all hope that in the area's that you can't see, the rust is equally OK, but only and endoscope will tell you that (bottom of A/B/C pillars)
'Bad' as in you don't know how well the welding was sealed up. And the welds are crude and don't look nice. Rustwise it may be OK-isch if the PO generously cut out the rust, cleaned everything well and patched on fresh edges and sealed everything well. That would be effective; structurally you're OK, rust-wise not bad; but she's isn't the best looking girl in the class anymore.
If the PO just welded a plate over the rust, and only painted the front, then you'll have a hole in 5 years.
Downside of getting those areas all crisp and well is 200 hours (plus minus a hundred) of sheet metal work.... It does look however that your fenders have been replaced, as the patches are stuck under them; i cannot imagine anyone doing that 10-15 years back without buying new fenders as they must have been rotten beyond patching as well. So those fenders are likely quite OK / salvagable.
Now as I don't see any signs of the welds rusting through, and if the repair has been a while back, then I think it has been done crude but effective as the rust has been kept dormant; I am in with the advice of
@Markos ; drive it!
example pic: it looks like this lower A-pillar has been horizontally split in two; rough welds visible, but nu rust holes.