Actually, I could see there being equity with a partner who brings the entire down payment, even if you do borrow the other 80% from the bank.But since you're asking about cash flow split, keep in mind that is different from equity. 

I also have the option of having a parent co-sign or being a co-borrower and definitely being able to get financing, but am going to try to secure the loan on my own first.

My opinion:  The only way working as an appraiser will give you more knowledge for your flipping business is if you target appraisal companies that work for lenders that specialize in construction loans and use appraisers/inspectors to inspect & approve work for a borrower to receive the next draw.

Of course you would expect a borrower to default on the second before the first but the second will get wiped out by a foreclosure on the first so its imperative the second forecloses first or all is lost. 

That's how much you can borrow --- in general.

Are you familiar how strict the sponsor requirements are, specifically borrow must have net worth exceeding loan amount. 

What options do I have as I never borrowed before.

While technically that’s true, but if I borrow someone’s money I feel a heck of a lot more responsible for making sure that money comes back!

Without them, people without the means to borrow six figures will not have any place to live. 

Debt is more limited in the upside, but its payments gets first priority from cash flow and is usually collateralized in some fashion (i.e. the debt holder gets something if the borrower can't pay, like ownership of the property itself).Your situation seems different in a few ways.