My initial question is… Is it good or bad to have individual septic for each mobile vs one big central unit??

A prudent investor doesn't seek quick riches through shortcuts.

i do think it's challenging, though, for a brand new investor with zero experience to jump right into a huge rehab with a contractor they've never worked with before.the contractor might want a larger up-front payment to mitigate their own risk, and they're not going to be interested in any kind of fancy nonsense like a 'penalty' when they know a new investor has never managed a large project before.i have also found that some contractors, including reputable ones, don't even want to share itemized bids because they just don't want to have to argue about the individual line items. 

It's great to hear that Rich Dad Poor Dad inspired you, it’s a classic for getting into the real estate mindset.

There are plenty of investors in bay area who got rich by holding negative cash flow properties over long time.

Separate LLC per Property: Maximizes liability protection but adds complexity and costs with individual tax filings.3.

My best advice would be to read through the contract carefully (builders usually have their own individual contract that's written for them and is leaning heavily in their favor).

As a self-employed 1099 individual, your best route is most likely DSCR.

@Nold R.In addition to the great post from Dave, possibly consider an option where the property is taken out of the LLC sooner rather than later and held as tenants-in-common prior to the sale, possibly setting you up in a position to take your share of the proceeds and individually purchase a replacement property via 1031 exchange. 

and connecting with local REI individuals and attending meetups to learn from experienced investors.