There is a certain rule that if your PhD degree is more than 6–7 years old, you cannot apply for a postdoc position.
Suppose a physically and mentally 100% fit 70-year-old person obtained his PhD degree in 1996 from Southeast Asia. He then worked as a teacher in two tertiary public institutions for 21 years, and he is now retired from public service.
Now he wants to get involved in academic research again in the EU.
How can he do that? Can he get paid for the research?