The benefit I can think of is that I'm getting a much lower rate because it's my primary house, the cons is that I'm taking a big loan, and even it has lower rate, the principal is much higher.My current interest will be 560K (rate of 3) + 150K (rate of 5, if I put 140K down), if I do cash out refin, it would be (850K rate of 3.75)Any suggestion is appreciated!

Also if so what benefits did I actually sign up for because it seems exactly the same as the free account.Thanks so much for your time :)

If he's telling you this before he starts work I'd give him the benefit of the doubt that it's a misunderstanding and I'd consider his new price.I don't know enough details to give you advice but based solely on what you've said I would stop everything until this gets worked out.  

Again, I don't have the facts here and I'm not giving you legal advice, but I think you might benefit from talking to an attorney and getting this all sorted out. 

As long as the numbers work, it will be to your benefit to secure as many units as possible with that cheap 30 year traditional financing while it's available to you.

What benefit do you get from a business account that you don't get from a personal account?

I didn’t think about the benefits of PMI.

The seller gets the benefit of enjoying interest payments, which will give them more of a profit than a regular sale.

Finally, I usually will consider about a .5% appreciation rate per year for overall appreciation (non-cash benefit, but can come in handy down the road), increases net worth slowly without taxes.Hope this helps as well. 

Tax benefits are also amazing, but don't let them dictate your analysis.