Proof of Funding when buying RE

[Rohme Williams]

So, if you find deal and tell your agent that you want to make an offer, when he asks "Do you have proof of funds"? Is it customary to ALWAYS have the funds, or can you hopefully have the offer accepted and then"find" the funding for the property after the offer is accepted? I have heard from multiple webinars, podcasts, and books that people have put a piece of property under contract AND then went out and found the cash/money for the property. Curious!?