Used to could buy it.

source: 
LAGS
Entry: 
629
Example: 
Used to could buy it.
Modal 1: 
used to
Modal 2: 
could
Gender: 
Female
Race/Ethnicity: 
Black
Age: 
61
Level of Education: 
8th grade
Home Community, Town, or State: 
AR (Little Rock)
Location Collected: 
AR (Little Rock)
Year: 
1975
Relation to Addressee: 
subject to fieldworker
Medium: 
Spoken
Sentence Structure: 
1.0
Status: 
Naturalistic