Source: Jessica Simpson, Eric Johnson Will “Definitely” Have Prenup

 Kevin Mazur/WireImage.com

Jessica Simpson's fiance Eric Johnson is in it for love — not money.

Slamming a tabloid claim to the contrary, a source close to the engaged couple tells UsMagazine.com that Johnson, 31, "is not a gold digger."

Exhibit A, the source points out: "There will definitely be a prenup" for the pair.  "Jessica has said she wants one. Jessica and Eric have talked about it," the source tells Us.

Indeed, there's a lot of dough at stake: The Jessica Simpson fashion/accessories brand grossed about $750 million in retail in 2010 alone.

"[Eric] understands that there needs to be a prenup," the insider explains. "He's supportive of it."

After dating for less than six months, ex-NFL pro and Yale grad Johnson popped the question to Simpson, 30, on Nov. 11.

"He really loves her," the source continues. "He's a low key guy. He's not into the glitz and materialism of Hollywood at all."

VIDEO: Jessica shows off her $150,000 engagement ring

The singer-turned-mogul herself gushed about her husband-to-be to Us last week.  "Every day is a romantic day with him," Simpson said at the Rockefeller Center Tree Lighting bash in NYC. "I'm very blessed."

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