You do know that the lifetime salary for a former president is something like $400,000 a year right? That alone prevents him from being classified as dirt poor, not only that but all of the under the table deals he pulled off as president I'm sure are ensuring that he retains what any normal American would consider to be a substantial amount of wealth.

Although, I do agree with your contention that he is very likely not a billionaire anywhere except on a sheet of paper somewhere, and chances are either he or somebody he employs wrote that sheet of paper specifically to ensure that it said he was a billionaire, so my bad.