We thought he'd just go as Batman!

Ben Affleck dressed as Donald Trump to trick-or-treat with Jen Garner and the kids last night, and his costume was pretty spot on! He rocked the POTUS' signature blue suit and red tie, and had a mask with the Prez's face on it, but didn't really want to be seen wearing it. We don't blame him! The actress went a little more low key in a spider web cape. Cute!

Earlier in the day, the Oscar winner checked out a home for sale just two blocks away from Jen and his brood's Pacific Palisades pad, and sources tell us he's going to buy it!

Our insider tells us:
    "Ben has looked at a lot of properties, but this one is perfect. It's never been lived in and its still under construction, so Ben is going to customize the finishes to his liking. The main thing he was looking for in a home was close proximity to his children, and now he's just down the block. He loves the idea that the kids can walk back and forth from his place to Jen's house. With a $10 million price tag, this one is also more practical that the one he fell in love with in the Santa Monica mountains."

The big question is... how is Jen going to feel about having his mistress-turned-girlfriend Lindsay Shookus practically living in her back yard? We'd be SO pissed! They've always put their co-parenting duties above any drama, so we guess she's OK with it!