Once everything is out in the open, I will be very, very (VERY!) surprised if drugs are not involved, at least in some capacity. There are so many theories and it could go so many different directions: (1) MC knew that JF was heavily involved in using or dealing and threatened to "out" him to WC who might then kick him out thus cutting off his financial security (even if it wasn't all that "secure", but at least a place to stay for free); (2) MC knew that both JF and WC were involved and was going to tell dad, move in permanently with him, and cut ties with WC; (3) MC herself was involved with drugs either using or dealing (the car wash theory that someone else told us about?); (4) MC was naive and wanted to "try" drugs but hooked up with the wrong person; (5) . . . and the list goes on . . .
Remember folks - drugs do not always mean street drugs like pot, meth, cocaine, etc. Prescription meds are becoming a HUGE problem with the young crowd these days, and frequently there are no tell-tale signs that someone is abusing them. That does not make them bad people - just people with problems.
All SPECULATION, and MOO.