Darren Fichardt, who won the Dimension Data Pro-Am in January, joined Thomas Aiken in a tie for third at 8-under-par 64. Tyrol Auret was one shot further back at 7-under-par 65.
Wessels jumped out of the gate on Thursday with birdies on each of his first three holes.
The 43-year-old started the back nine equally as well with three consecutive birdies starting at the par-4 10th.
Wessels then birdied the 14th and closed with back-to-back birdies from the 17th for his share of first.
'I've been doing this for 20 years and have become tired of the constant travelling and the huge commitment to practicing,' said Wessels. 'My priorities have changed and I want to spend more time with the family.'
Simon had a few streaks of his own. He picked up his first of four consecutive birdies at the par-5 third and added a birdie at the eighth to make the turn at 5 under.
He moved to minus-6 with a birdie at the 11th but found trouble with a bogey at the par-4 13th.
Simon responded well and caught fire down the stretch with birdies on each of his last four holes.
'It's still quite difficult,' Simon said of the course. 'But I was just being positive from tee to green.'
Craig Lile, Hennie Walters, Bruce Vaughan, Louis Oosthuizen and Alan Michell share sixth place at 6-under-par 66.
Patrick O'Brien, Dean van Staden, Warrick Druian and Ashley Roestoff finished knotted at 5-under-par 67.