The sentence is self-contradictory. Either it is very difficult or it is impossible. It can't be both at the same time.
In American English a common expression to set up such a communication would be "I have about as much chance of becoming a millionaire at my age as I do "______________". The blank can be filled in with any unlikely event for a person of advanced age:
- Winning the Olympic Marathon
- Getting "carded" at a bar for being underage
- Winning the "American Teen Idol" competition
- Having Brad Pitt's love child
The idea is to get a laugh out of the hypothetical circumstance (not that I have any talent for this, so pardon the examples.)