Kris Humphries Mother Moving Into His Building

Sources close to Kris tell TMZ ... following his parents' divorce, his mom moved out of her house in Minnesota -- and started crashing at Kris' pad in NJ.

But TMZ broke the story ... Kris recently moved to a swanky $8k/ month condo in NYC when the Nets moved to Brooklyn -- and now his mom is following suit.

We're told Kris is footing the bill on the rental (which is NOT on the same floor as his) -- but Mama Humphries DOES have a key to his apt ... and likes to show up unannounced sometimes.