A lawyer for the former TV journalist has roped in a private eye to dig into the former Governor's secret past and deep finances, including whether he fathered more than one child out of wedlock, as has been speculated.
Shriver wants to know exactly what Schwarzenegger is worth, a source close to the case said.
"Maria is leaving no stone unturned and she has authorized a private detective to gather personal and business information about Arnold," the insider dished to RadarOnline.com.
"Maria needs and wants to know exactly what she is dealing with.
"The investigator will likely like into the claims that he fathered multiple children, outside their marriage. Maria has heard the rumors and she wants to find out one way or another, if those claims are true."
The investigator will also sift through the secret money trail the 63-year-old True Lies star orchestrated to funnel to housekeeper Mildred Baena, 50, the mother of his secret son, now 13.
"Maria wants to know exactly how much money Patty received from Arnold... she wants to know everything, period," the insider said.
Until this move, it had been suggested that Shriver, 55, hadn't yet decided yet if she wanted to end the pair's turbulent 25-year union due to her strong religious faith.
The Catholic Church does not accept divorce.
But RadarOnline.com has been told Shriver recently arrived at her decision that she needed to uncover the sordid details of husband's double life herself.
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The power couple's worth has been assessed at anywhere from $200 million to $800 million.
The pair is believed to have a pre-nuptial agreement.
But if the pre-nup does not stand up in court, in the event it is challenged, the couple would likely split their net worth evenly, under California law.
One legal source suggested Shriver also would be entitled to whatever the philandering star-turned-politician spent on his mistress.
In California, all divorces are "No Fault" divorces, meaning the spouse asking for a divorce does not have to prove the other spouse did something wrong.
"But any money that Arnold spent on Mildred, for her house, or any other payments or gifts he made to her, Maria is legally entitled to," the source told RadarOnline.com.