They are often referred to as a Key Principal.Now back to your questions: No, it is not necessary to have a sponsor as part of your GP, but arguably it is common.  

I don't think you don't need any permits to add a bedroom/bath etc. if it's a single family home, you can arguably change anything within your structure (or outside but adding more structures/buildings needs permits).

Arguably no other benefactor in L.A.’s recent memory wielded Broad’s name recognition, clout and influence.

However, "house hacking" is always a great (arguably the best) option to start!

What are the advantages of having one (arguably there are no costs that can't also be obtained with an umbrella liability insurance policy) versus the costs (yearly registrations, extra paperwork, startup costs, more expensive mortgage options)? 

It is arguably a perfect property for me with the layout (it also has a large detached garage I can run my online retail business out of), which is uncommon, but there have been others that would work.

Don't get me wrong, I still like nice things, arguably more than most, I definingly have my diva streak who loves flying 1st class and all the shiny fancy things, it's just that I have wired my brain differently in the how to obtain method of this. 

Lastly but arguably the most important part, a question I hear time to time which is both gratefulness for my time invested to freely give here to others, but also confusion and a bit of shock as to why a person of my standing would be here, doing this, vs selling out conference rooms and charging $495 per person for a 3 day session as I did for years.

Therefore adding 100 square feet is arguably only worth $20,000.That's why looking at comps is so important. 

You should post this on Medium but I’m sure those in the RE education business (arguably racket) would attempt to undermine the knowledge you shared today.I’ve been doing this for 20+ years and knowing what I am and when I’m in the other categories has enabled me to be relatively successful in Real Estate.