My first "High End" flip -- Looking for some input

[Alvin Uy]

So here's where I am with this.... 

A couple of weeks ago, a close personal friend reached out to me about an off-market property she picked up in Eagle Rock, Los Angeles. She is now on escrow using a loan to purchase with 20% down. Her original partner on this deal (who was going to finance the downpayment and rehab) dropped out last minute. She was trying to do the project alone, but her funds are tide up with other projects and her personal cash injection for her downpayment did not meet the lenders "seasoning guidelines" to close the deal. So she reached out and asked me if I want to jump in to help salvage the deal and not lose her EMD. I should mention she runs a construction company and has other High End projects in the works.

Here are the property details:   Its a small 3/1 SFR (1200sqft) on a big lot zoned for 2 units in a hot area of Eagle Rock walking distance from Occidental College (prime area lots of high end homes). Purchase price at $835K (but comps are at $1M). I should mention the house came with approved plans for 2 houses but seller decided to sell instead.   There are 2 other "high end" flips on the market within a half mile listed for $1.65M & $1.98M. One is a 4/2 SFR + an additional Studio ADU - total is 2500sqft. The other listing is 2 unit is 4/2 house + 1/1 guest house - total is 3300sqft.  I was told that one for $1.65M just received multiple offers some above asking price. The other one just listed a week ago but is getting a lot of traction.

Here is the plan:  We will expand the 1st unit to a 4/2 and add a 3/2 guest house in the back from ground up... totaling 3440sqft (max allowable build size on the lot).  Total construction with high end finishing+holding costs estimate is about $450K max. Target is 8-10wks build time.  We plan to list conservatively priced at $1.75M-1.85M (if you can call this price range conservative LOL!).   Potential Net around $450k-550k to split between us.

I will be quitclaimed on title at end of escrow this week.  All funds for acquisition/construction/holding costs will be split 50/50 and so will the profits.   Being that this my first "high end" flip with big potential gains... Im wondering whats the best way hold title and the best way to navigate/optimize my taxed position.  I've been a "buy and hold" investor with all the properties I've bought under my name.  This is actually my first ground-up and "high end" flip under my name so I have some things I need to work out and need some perspective on:

1) Tax-wise, what is the possibility that I could get away from not being classified as a "dealer" given its my first flip?!?!  

2) Not going to hold title under my name of this for obvious reasons.   Im thinking It's too late to file a new LLC in time for the escrow, but I do have an S-Corp available that I can use... the only rub is it sounds like a real estate company so not sure if I can get away from being assumed as a "dealer" with the intent to flip.   Is this a good idea?

3) I should mention I will be leveraging my HELOC (5.7% interest rate) to finance this... roughly $435k max to cover my end. HELOC is obviously under my personal name. Can I still use this if I hold title under the S-Corp?

My CPA is out on vacation at the moment and won't be back until after closing...  This is moving fast, I can really use some input and expert advise.