When do the side effects start after saying the spell?

Answer 1

They are superstition, so don't expect too much.

A Pagan Perspective

If by "side effects" you mean the actualization of the spell, then you may have misunderstood the idea of a spell.

A "spell" is one of the manners in which a practitioner performs "magic".

"Magic" is simply stated the manipulation of naturally occurring powers and forces, by the hand and will of a (hopefully) ethical and trained practitioner.

Just saying the words, without the "rest of the work" usually has little or no effect. Properly done, magic can and does manifest the desired result.

That said, I recommend you look into the Threefold Rule, which states, "That which you send out will return to you threefold."

It has been my experience, that the Threefold Rule is remarkably swift in taking effect.

So if you are wondering about that as a "side effect" I'd be inclined to say it will be taking effect "about now".