I have an incredible opportunity for a SFR flip in the San Francisco Bay Area with an estimated PROFIT of $500K!

First off, until you take an action like sell or refi its just an estimate of value.

Otherwise, it will be hard for builder to give you any estimate. 

I have 3,200 in liquidity and I estimate I should have north of 5,000 before the school year is over(we have been flipping furniture on Facebook marketplace and have made nearly 1,000 in the past 4 weeks). 

Essentially the homeowners did not lower the price, but they agreed to fix the window issues after showing them and estimated the cost for all other repairs. 

If you take out the land value, the remaining amount should be an estimate of the depreciated value of the house (ACV).  

There was no structural engineer assessment, but their bid/estimate process was thorough & articulate: measuring the slope of each corner of the house from the center point on the main level, explaining Pin-piles vs.

Zillow rental estimates are nice but I have thought about contacting some PM companies to see what they think it could rent for as is.

OR we can finance it with cash (in the form of heloc or hard money), rehab it, and cash out re-fi at 75% LTV after 6 months with estimated ARV close to 450k , that will allow us to recover about 90% of total cash invested, we are leaning towards the cash route, but want to run in by the more experienced to make sure we are not missing anything.

Rough estimation here.