Infact, I've seen more than enough times that the historical calculation become so far ingrained in the future that you were better off viewing it as an entirely irrelevant.  

Anyone have an idea of whether this is a mistake in the book or my/Google's calculations?

I have use the calculator on Bigger Pockets but it only allow for dollars instead of % to calculate.  

However 2 things to note: 1) DSCR loans for future investment property acquisitions do not care about your DTI (DTI only really matters when buying a new primary or any time you are using a Fannie/Freddie/Ginnie loan).  2) After 12 months of proof of someone else paying it for you, you may be able to omit it from your DTI calculation. 

Can they explain how they calculate their vacancy rates?

Option 2: I found a house that the asking price is 930k , but I’m sure I can get a discount on it because it needs a lot of work , it doesn’t qualify for traditional financing , so I would need to take a hard money loan , it needs about 150k worth of work , the plan would be to offer the full 930k asking price but ask for a 6% seller concession , I calculated 20% down payment and 7% closing cost , so total after seller concessions comes out to 21% down payment which is $195,300 .

FHA might work, just get out the spreadsheet/calculator to figure out if the extra PMI is worth it, or even feasible. 

You are also short on your expense calculations. 

Leverage can be a great thing but its a calculated risk , and a lot of people put too much faith on the upside and little consideration  for the downside .

Debtor must clearly phrase their request to obtain: the source of a debt and the amount a bad debt buyer paid for plaintiff’s debt; how amount sought was calculated; where in issue a list of reports to credit bureaus; and documents conferring authority on third party to collect debt.Documentation of the creation of the debt with your collection agency.Under FDCPA Section 809 (b), you are not allowed to pursue collection activity until the debt is validated.