I have been told that I can have my name put on my parents card as an authorized user and then that would start building me credit, is this true? 

As you observed, getting the deed is the easy part: There are insurance issues, payment challenges, 3rd-party authorizations, etc.If you reach out to me directly (I'm rarely on BP anymore), I'll gladly share my recommendations.

If the tenant is trashing the property, the current PMC may not be doing their job, but we don't know what the seller has authorized the PMC to do.

In 2009, Mentore purportedly executed to Nykian a second power of attorney with expanded authority.

The other option after that would be look up the City municipal codes, specifically for the regulation authorizing a casita on a SFR parcel.

If a broker or a lender originates and funds a loan (either from their own funds or on a warehouse line) that doesn't conform to the current zoning and it doesn't have "legal non-conforming" status with an explanation of the current zoning on the first page of an appraisal form 1004, and subsequently a 100% rebuild letter from the zoning authority, that loan is considered "unsalable". 

We are trying out use of Landlord-Tenant Authority Forms and waiting for results. 

But when searching for an entity, you still have to list yourself as an authorized person / member so in the end is there really any point to get a virtual office address?

I talked to the seller,  (a lawyer) who had the same opinion that I had: The improvements were made before we had walked through the property and they weren't authorized by the landlord.

I am reading a book that may be of interest to you: the author develops high end mansions in southern Florida.