How remote the chances are of making money from a startup depend on the person. The probability ranges from a snowball's chance in hell to maybe 90% in the case of someone like Bill Gates. (He was not necessarily going to be the richest man of all, but the likelihood of him not even making enough to be independently wealthy was pretty small.) I can't tell what the chances would be in your case without meeting you, but certainly there are some people for whom starting a startup is a reasonable gamble.
It definitely wouldn't take decades to find out. When startups fail they usually fail in less than 2 years.