I suggest asking the LL if you could buy the lock for the front door and whatever else is needed and ask if she would knock the price of what you paid off the rent.
For instance:
You pay $1000 cash for the rental of the apartment per month
You buy a doorknob and lock set for $60
You give the landlord $940 cash and a receipt for $60 for the lock set as rent for the month of August 11
If your in need of several hundred dollars in repairs you can also tell the landlord that you will do a few repairs every month until the things stated are corrected, so you don't have to give her $300 cash and a receipt for $700 for the rent.

