BUM
Thinks s/he gets paid by the post
Skip the legal dance ... allow the living arrangements you describe but keep the place in YOUR name.
UPDATE
The concept is still chugging along but the plan is slowing morphing
Well it looks like we will be closing on house #1 in a couple weeks (I keep saying that) and moving the kids into our big house. No ownership changes for now. The kids will pay all expenses except taxes and HOI which we will split. Accounts like cable, electric, telephone, trash removal, etc. are being put in their names. DW and I will pay our estimated share of the utilities when we are in residence.
I've remodeled the basement, added a kitchenette. Already had a half bath, bedroom and office area. Now a quiet, comfy place to sleep, snack, read, watch TV, escape, whatever. The main floor is designated as common area. We will share kitchen, LR, DR, and den and the upstairs (3 BR) is for the kids.
Once we get them moved in, we are outta here! Heading for the beach, be back around Thanksgiving... thats the plan, so far. Everyone is excited.