As several people mentioned above, the only break ins I've had to deal with were people kicking in doors or breaking windows- locks are only one small component of security.

I am a 21 year old looking to make real estate investing my career.

Should I keep this money maker, or should I sell it?

I am leaving my current job to make real estate my full time career, I have experience in apartment leasing, tenant selection and screening as well as construction including door and window rehab / installation and blind installation.

We are definitely in door-acquisition mode!

The other issue was that most of the time, the names given were not decision makers so the advertising effort would basically fall on deaf ears.  

Which do you think has the best return for the time put in - Door Knocking, Cold Calling, Attending Social Functions, or something else?

While in my new role as Home Maker (still getting used to it) I would pursue entrepreneurial projects, including real estate.Therefore I'm trying to come up with creative strategies to invest in real estate while not working.

Does this seem to be potential money maker?

If your lender is a big bank or hedge fund, it might be difficult to get in contact with a decision maker since your loan is performing.