There are statutory guidelines that are based upon the gross income of each parent, the number of children, the extraordinary expenses of the children, and number of nights a child spends with each parent, which are adopted by states in order for the states to be eligible for federal welfare programs; although standards vary somewhat. Income can be imputed if a party has an ability to earn income but does not exercise it. But, assets owned aren't considered unless they produce or could produce income.
In the absence of a showing of unfitness sufficient to terminate the parental rights of a parent for abuse or neglect, or some extremely unique circumstance (e.g., one parent is on the space station 365 days a year), no parent ever has 100% of the nights with the children.
Without having a more realistic estimate of the number of nights with each child, and a fair guess of the capacity of mom to earn income including income from stock trades, it isn't possible to make a realistic estimate.
To get the correct estimate, you would need to do a full fledged child support guidelines calculation, but this question doesn't have enough information to do that. A good rule of thumb is that child support for two children is typically about 25% of the difference in income of the couple times the number of days that one parent has a child more than the the parent, divided by the number of days in the year.
For a pretty typical parenting time division, that would work out to about 10% of the difference in income between the parties paid by the higher income party to the less high income party within a normal range. But this is strictly a rule of thumb.
However, in a case like the one you describe, the rental value of one of the houses would probably be imputed as income to the wife, as would the profits she makes in an average year from stock trades. The rental value of a $1.25 million house is probably about $72,000 a year. It is hard to value stock trades which depend upon the size of the portfolio and the skill of the trader.
If the stock trades generated $28,000 of income a year and the wife has the kids 5 nights a week, and there were no extraordinary expenses, child support might typically be on the order of $416 a month. If wife made $78,000 from stock trades, child support would be nominal (they would have equal incomes, but she would have a few more days a year).
But, that involves some very specific assumptions.
Also, in situations like this one where the facts are so extraordinary relative to a typical divorced couple and the family is very affluent on a combined basis, the judge has wide discretion to deviate from the guidelines on a case by case basis. In reality, no case like this has a clear fair or typical resolution and it would depend a great deal upon how the case was argued and how the facts were developed by the parties and their counsel.