I thought I had done all my research. Passport, tickets, etc......no visa for us citizens if staying under 30 days...

Then today I came across several websites that said that you needed something to prove
" financial ability to maintain yourself during your stay..."

I would have THOUGHT that prepaid hotel, airline tickets would have been quite sufficient. Do you know what the deal is here? I have never had this requirement anywhere I've traveled (but I know that there AREA places where you do need this).