Of course, Hard Money is higher but hopefully there is a win/win compared with the slow pace of Banks.

Comparable rentals that come on the market in my area are rarely active for more than a day.  

If I want to make a formal offer and ask for seller financing do I use the traditional purchase and sale agreement or do I need an attorney to draft specific paperwork with my term?

Your bank will do their own appraisal (and since this is a duplex, the appraisal will be based upon comparable sales) and then offer you the HELOC based upon the results of this.

It was crazy to think when comparing the risks, how less risky a duplex was vs the 10 unit (huge old building/a lot of operating expenses)The prior 3 years only grossed $75 k on avg which would mean we would lose in first year if it did those numbers.  

I’ll still be building equity with the help of a tenant, I’ll have my foot in the door and I’ll be saving 480/mo compared to my current circumstance. 

I'm assuming you can't go out and get traditional financing?

I’m going to base the cashflow on a traditional tenant even though my strategy is short term vacation rentals.  

The time that they spent on the sideline has opportunity cost (rents, loan pay down, appreciation, etc) compared to if they just bought something off the MLS.

They find a total average return of 9% for the period they looked at (1986 to 2014), and conclude:"Each component contributes approximately equally to the aggregate U.S. portfolio of housing returns, so excluding one component excludes half of total returns on average," There is also a helpful graph comparing the breakdown between the two factors in the 30 largest metro areas.