I agree with with Shrub about too many door openers.
Locksmithing is a huge subject and covers many different areas of work, trying to survive on just lock outs would be a very big ask, if you could identify a specialist area which is lacking in your Yellow Pages then you could maybe concentrate on filling that gap.
BTW I am very busy at the moment and have been for the the last few months. (Mainly jammed UPVC Doors).
Mark