Whats a good offer price?

[Dena Zeid]

Looking into my first potential flip in ny.   I'm new and want to make sure I don't offer too high a price.  Here's the financials:

Selling price: 280,000

ARV= 380,000

Rehab costs= 40,000

Offer would be all cash.  

What's the maximum allowable purchase price for this deal?  I know according to the 70% rule it should be less than 230,000, but I don't think I would be able to get any deal if I focus on the 70% rule.  What percent profit is factored in the 70% rule?