Apart from normal wear (brakes, clutch, shocks etc.), the only major problem was a leaky fuel tank because of serious corrosion.
Rust is also a problem at the body, but it is manageable when you don't wait too long.
This was one of the best-selling cars in Europe in the late 70s and early 80s, because of its many virtues:
It wasn't expensive, neither in purchasing nor in maintenance (and it still isn't).
It is very roomy and comfortable.
With the top engine (110 hp), it really was a fast car.
It was available in many different versions from basic and simple to luxurious or sporty (in Germany even a version for hunters or forest wardens was available)
Although its overall appearance is hardly modern, it still has a rather timeless look (most people estimate the age of my car at 10 to 12 years, while in fact it is 28 years old!)