GRINNELL, Iowa — A for-profit company has proposed turning a boarded-up former nursing home here into a psychiatric hospital, joining a national trend toward having such hospitals owned by investors instead of by state governments or nonprofit health systems. The companies see a business opportunity in the shortage of inpatient beds for people with severe mental illness. The scarcity of inpatient psychiatric care is evident nationwide, especially in rural areas. People in crisis often are held for days or weeks in emergency rooms or jails, then transported far from their hometowns when a bed o…