Brooks, who has never finished in the top 10 on the European Tour, held a one-shot lead over Frenchman Francois Calmels.
When play was suspended for the day, however, 57 players had yet to start their rounds at the Mount Edgecombe Country Club as torrential rain fell.
Organisers shortened the fifth hole to a par-three from a short par-four after moving the tee to avoid the water.
Brooks, who had a bogeyless round with four birdies on both the front and back nine, finished just before play was halted.
Calmels, who led a trio of Frenchmen chasing Brooks, shot a seven-under 63 which included an eagle on the par-five 14th.
A shot further back were his compatriots Edouard Dubois and Romain Wattel.
Last year's inaugural event was shortened to 36 holes after persistent rain but the forecast for the next few days is more positive. Scott Jamieson of Scotland won the title in 2012 but he has yet to begin his defence.
The start of the tournament was brought forward 24 hours to avoid a clash with the funeral of former South African president Nelson Mandela on Sunday in his boyhood home of Qunu.