I would only use the more toxic chemicals as a last resort and only with special precautions such as a padlock on the attic access to prevent accidental access by the small children or pets.

In addition and depending on the written terms, this may or may not include utilities.The rents paid by HUD are super desirable in a region like the DMV, however; I would caution you to take the necessary precautions that you would take with any other tenant, i.e. rental history, credit check, background check, and if applicable, employment verification.

If they’re in my unit, I️ prefer them to be on month to month as a precaution.

Has the owner kept the heat on and taken the precautions necessary so the pipes don't freeze?

Still serve the notice as a precaution. 

You will need to take safety precautions if allowing people into your home.

Are there any other precautions I should be weary of?

As others said, run a background check for those people and add them to lease if possible.Those are precaution for worse cases, when things go sound, you want to have lease to protect yourself.

If so what precautions would you take...is getting a double security enough and doing month to month for the lease?

Don’t get me wrong, I have seen some neighborhoods in those areas that have cleaned up, just have to have precaution.