Why?

Bill's Humble Abode

Bill grinned widely. Not an evil grin, however, it was a genuine, happy grin. "So, why do you want us to stay anyways?" Dipper asked. "I-well...I don't have any friends..." As the blonde said this, he hung his head solemnly. "Oh, Bill.."Mabel said, mourningly.
"A-anyways....um, follow me! You can come to my house and..and hang out! O-Okay?" He kept on looking over his shoulder, as if making sure nobody heard. "Uh-" "Sure!!" The female interrupted.
Bill smiled, "Uh, great! Let's go...come on!" He stopped as he saw that Dipper wasn't moving. "Dip-I mean, D, what's wrong?" "I, um, can I talk to you for a moment?" Mabel nodded and walked back over to her brother, where Bill couldn't hear. "I don't feel comfortable around Bill, Mabel. He looks like he's going to kidnap us or something.." "Come on Dippingsauce! He's not gonna hurt us," She gestured at the boy who was now pawing the ground with his foot,"did you see the way he looked earlier? He has no friends, and we need to fix that!" Dipper smiled in understanding and nodded. "Alright Mabel, let's go..."
The trio walked down the street, wondering where a future demon could possibly live. Did he live in a shack, or an old dump like Mcgucket? After a couple minutes of walking, the three stopped in front of a large two story house. Did I say house? I meant mansion. It had yellow shingles on the exterior walls and about 15 windows (a rough estimate made by Dipper). It's roof was a creamy, white color and the chimney was a metallic filter, spouting small amounts of smoke into the air, it looked a lot like Pacifica's mansion, just more bright.
"Whelp, here we are!" Bill smiled, expecting the twins to exclaim about how big it was, which, after recovering from their shock, did. Bill led them into the two story and showed them around, eventually ending up in his room, and what a room it was!
The room was medium sized, a king sized, red four-poster bed in the middle. The carpet was the same color as the roof and seemed to have been vacuumed recently. Two windows were planted in the wall, on the left side. It's curtains were a shade of red velvet and were hanging so that the bottom almost brushed the floor. A wooden bed table stood on the other side of the bed and, right beside it, a wooden dresser stood proud and tall. A golden lamp stood atop the bed table and, by the looks of it, it was genuine gold.
Both twins stood in shock but then Mabel smiled. "It looks like this room's fit for a prince!" She shouted, making a running jump onto the bed. The blonde just smiled at this and sat himself down on the bed, Dipper still standing in the doorway. "Well, what're you waiting for, an invitation? Come on D!" He patted the bed beside him, gesturing the brunette to come and sit which he did.