Botha must pay this amount in maintenance for Francois Jooste, a 22-year-old Tukkie, his illegitimate child with Anna Edwards.
Jooste sued his father for, among other things, university fees and living expenses, because he is a student and does not work.
Botha paid maintenance for Jooste until he was 18 years old and then stopped paying.
Chief Magistrate Desmond Nair found in the Pretoria magistrate's court on Monday that Edwards suffers from a heart- and blood condition and as such cannot support her son.
Jooste is a second-year student at the University of Pretoria, where he is studying computer engineering.
Jooste said in a statement to the court that his degree course costs over R25 000 per year. His total monthly expenses amount to more than R12 000.
This includes his accommodation, food, university fees, books, internet account, gym membership and a laundry account.
Nair also said that Botha had not disclosed his income to the court. "Botha's ability to pay reasonable maintenance is not being disputed here."
Jooste left the court with a broad smile on his face after Nair's verdict.
Jooste's mother supported him in a damages claim against Botha in the North Gauteng High Court in 2000.
At the time Jooste claimed R450 000 for emotional distress and injuria because his father reportedly did not want to acknowledge or communicate with him.
The claim was denied, among other reasons because the court found that Botha does not have a legal duty to love his son or communicate with him.
Botha did not want to speak to the media after court proceedings on Monday.