Ja nee. P is quite right. On the long term cash is not king. Had you invested in stocks before the devastating 2007/8 markets crash, you would still be better off now than if you had cash in fixed deposit or the like.
When to buy is a whole new topic. Monthly subs as you intend to do is great but you would do very much better to not buy at expensive levels. This you need to learn by looking at a simple chart of the stock or index.
Bear in mind that you cannot time stocks but you can see if it is overpriced or cheap.
Had I listened to me now years ago, I would be quite wealthy by now. To be exact, I would have been 9 fold better off and my wife is still kicking my ass.
As to your tax remark. SARS has become very strict since efilling got itself invented. My rough guess is that 90% of efilling is computed and does not need human intervention. The ones that do are the self employed/traders/investors that book profits without an IRP5. SARS now has more time to investigate the 10%. Most now will be audited but the audit is simple. They ask for supporting documents. If they don't understand them, you will get mail stating that they accept your result but they reserve the right to redo the audit at a latter time but by then it would prescribe and you off the hook like me.