To be an investor in your 70's would require about a $10million investment! The investor category also has a points system, and the older you are the more cash you have to stump up.

Depending on how much family your parents are leaving behind, you may well be able to sponsor them. As fisheress pointed out, its a 'centre of gravity' thing, meaning you can sponsor them as long as they have more family in NZ than back home.