I understand your opinion. I THINK KB was certain she would not be living with PF in the near future. Otherwise, I don’t believe she would have purchased a home.
If she anticipated him moving in with her, I think she would have purchased a much larger home. 750 sq ft is very small, especially for a two story, imo.
If we assume 250 sq ft for BRs total & another 150 for bath/kitchen, there virtually no space for a third person, imo.
Also, idk that KB did NOT want to live at the “ranchette”. Reportedly she enjoyed horses, outdoors, etc. I think PF did not want her living there. He could easily have said “mom won’t allow it, she owns the place”, & I do think he might have his own place in a barn.
Jmo