"Zac nearly drained his bank accounts partying, so he's pretty broke while he waits for his profits from Neighbors to come in." reveals an insider. "He told Michelle that he couldn't afford to go to Europe, but she wanted him there and was happy to pay for his trip."

While pals of the Fast & Furious stat, 36, are worried that Zac [was] using her as a ticket to the good life, Michelle [didn't] mind playing sugar mama, at least for a little while. "Part of her may actually like paying, because it makes her feel powerful," says the source. "Plus, she's confident that Zac will pay her back when the checks start rolling in."