Taking a stab at a reasonable definition for me, if you receive resources X or less as financial or in-kind assistance, and you go from X to 100X through regular market transactions, you can say you're a self-made 100Xaire. 10X seems too liberal (after all, someone could have just invested the X at birth in an index fund and waited 40 years and be at 10X), while 1000x seems too restrictive (if you start out with $10k and end up with $5M, I think it's still fair to say you're a self made millionaire). It's probably not a truly linear relationship, though (it's easier to go from $10M to $100M than $10k to $100k).

This is probably a broader definition than the original comment's.