her lover (I mean, the coworker) can help build equity in the 2nd home. (If you make extra payments on the house using his money.)

Then, once the divorce is settled, there'll be more equity in the house.

AND, her adultery will give you leverage in settlement.

So, the pie gets bigger and you'll keep a bit more of the pie.

I'd stretch this deal out for a good 5-6 years so that his payments really buy down the mortgage.