An ANC, if choosing to go without accrual, is a fairly simple contract. It separates the estates, and excludes community of profit and loss from the marriage. An ANC with accrual, is a more complicated document, as it needs to set out starting values of each parties estates. In the event of dissolution, these need to be taken into consideration with a specific formula that factors in how much each party earned during the duration of the marriage.
Both however, has to be notarised by a Notary Public, and then registered at the Deeds Office in order for it be effective against third parties, else it is only enforceable between the two parties in the marriage.
Making the decision between with accrual/without accrual is your starting point. ANCs go for around R5k-R7k with registration for a without accrual contract, and will be more if you choose to go the with accrual route.
Just remember, cheap gets you what you pay for, and getting caught out on dissolution of a marriage (if you didn't handle these things properly) is a kak expensive exercise.
My advice... Get proper advice from an Attorney who is also a Notary Public, and handle this aspect properly.