Schemes can apply a percentage penalty on your monthly contribution if you join after age 35 and don't have at least two years of continuous prior cover. The penalty scales with how far past 35 you are and applies permanently; there is no way to remove it later, even after years of paying. It exists to discourage healthy people from waiting until they're sick to join.
SA example: A 50-year-old joining their first scheme: 15 years past age 35, no prior cover. Penalty is roughly 25% of risk contribution, applied permanently. On a R5,000/month plan, that's an extra R1,000+ a month. Forever.