I just checked out this calculator and done a bit of rough math...
If you delegate 1000 SP you will earn approx $16 per month. If you then added these profits to your delegated SP, you will almost double your SP in about 3 years time you will be earning about $25 - $30 per month. This is a rough estimate and it also massively depends on the market prices.

Don't get me wrong, these are MUCH better interest rates than you will find with any bank but you're getting this benefit because of the risk your taking.

Unfortunatly, like all things in life... you can make some easy money if you already have money. For example, if you had 125,000 SP (That's one hundred and 25 thousand SP) You would earn the same as a full-time job at the British minimum wage rate i.e £300 per week ($420)
That's how much SP I would need to give up work so that isn't going to happen any time soon.
However, that's because it's expensive to live in the UK. In other parts of the world where $5 a day is a good wage, you would only need 10k SP.
But that doesn't help anyone really because in these countries, it would be just as hard to get 10k SP as it is for me to get 120k SP in the UK.

Anyway, I'm not knocking SP delegation because it is free money but it's not a way to get rich.