Just take the interest rate they are charging multiplied by the money you are borrowing.

We take the full month's rent, divide it by 30 and multiply that total times 11.The reason we charge for the entire month the first month is because we don't want the tenant to use the apartment like a hotel room where they pay for 11 days and move out.I am fairly positive that if what you are saying is 100% correct then the landlord is not doing business legally.It is also very possible that the management company is doing the books, telling the landlord the apartment was rented for only 11 days and the management company is pocketing the difference.As stated, I would record the conversation and let them know.

I take the ARV and multiply it by 70%. 

Hello BP friends,There are multiply arguments I hear when I talk to folks about using hard money loans for rental properties.

Or multiply using your proceeds as down payments to get economies that way as well as the return boost from leverage.  

Instead of paying the "term" portion, more money just goes to the investment, so your money would multiply faster.

I've called the roofing company and they have came out to the property multiply times. 

Whereas a mobile home park in the middle of nowhere may go for a 12 cap because investors require a higher return for something that is much more management intensive with less appreciation potential.One might assume that a higher cap rate is always a good thing, however, if your business plan is to force appreciation by improving NOI, a lower cap rate multiplies the value of the improvements you made more than a lower cap rate based on the simple math of it.

Read this article here, I found it helpful when I was trying to understand everything. https://affordanything.com/one-percent-rule-gross-rent-multiplier/

So for your DTI they will multiply your monthly rental income by 0.70 and use that number.