How much rust is "too much"?

I want to restore my 1984 Celica GT, that I got recently.

Problem is that I don't know a whole lot about cars, but what I do know is that rust is bad... and I have rust.

I can post pictures tomorow, after I take some of the spots.

but maybe someone could answer my question without the pictures...

At what point does the problem become no longer worth it to fix? Because I would really like to save this car from being trashed.

Body parts can always be replaced and painted to match. Rust on suspension supports is a problem you can't easily solve.