It must be private or hard money lending, or cash from your own resources.But, while you can't take title to the new property you can have it under contract before you close the sale of your old property. 

My business partner and I have been coming across off-market deals and have a flip opportunity in Gresham and a lot in SE Portland for a new build.

I have been very impressed by their business plan and professionalism.  

-we were quoted some private flood insurance around ~$1800 for what we thought was adequate coverage for all buildings, underwrote that number, and moved onA little further along we learn the flood zoning is zone AE, private flood insurance isn't much of a thing for an AE zone, and FEMA flood insurance is expensive. 

I could be off here, but my understanding is that if you are already in the business, you have a precedent set and can depreciate furnishings as you scale your portfolio. 

If he wanted his business practices to be different, than they would be. 

Hi - typically Mixed Use properties are going to require a traditional commercial real estate loan from a bank, small balance commercial private lender or for the larger ones a CMBS style loan.However, a newer "DSCR Loan" product for Mixed Use is making a comeback - which is a really great option for smaller properties/more beginner investors since it has all the same trappings as a residential DSCR Loan (30-year fixed, easy qualification, straightforward process) for a property with commercial units.Generally going to be limited to 8 units max and has to be primarily residential in every way (majority residential by units, square footage and rents) but if it fits all that, its a great option

Im very new in the real estate business but i think youre right $500-800 dollars is better than $1500

If you are using the HELOC proceeds to acquire land for a property that will be business use in some manner (a rental), then that interest expense from the HELOC would be deductible against that business project.