For your existing primary, you will need to have it leased with the security deposit and first month's rent collected.

I inquired about the possibility of a two-company structure: A traditional LLC that is the public face of the activities (collecting rents, paying contractors, etc.) and managing the Series LLC with each property in once cell in it (in this case, Series LLC is serving as a holding role).Again, one attorney said that would be much better than a standalone LLC and that is recommended approach, and the other said it is waste of time and money since there are some requirements from Texas Real Estate Commission, which is requiring being a licensed broker in the state to operate in the managing LLC.So, just want to hear what other Texas investors are doing when it comes to series LLCs regarding these issues. 

While I have owned homes before, I have never house hacked so am looking into resources here on BP as well to learn more.

Quote from @Brian Bowen: Is there a good free method or resource to find owner contact information?  

My research guided me to form an LLC to hold the properties during repair/rehab (I am buying properties that need major fixing) and move them to another LLC where I will be collecting rent. 

In addition you can use it to collect initial security deposits or to bill the tenant for addition items such as billed back utilities, damages, etc.

Partner Driven utilized a combination of resources to fund this project, including capital investment and support from our partner, Preston Moore.

With a full time job even 15 units gets tough between collecting rent keeping repairs up, preventative maintenance, looking for new deals, managing refinances, etc. 

BiggerPockets is full of resources designed to help you along your journey, whether you are just getting started or a seasoned investor.

The only thing a tenant does it prove the rent you can collect as opposed to a proforma of suggested rent.