So I guess the same calculator could be used but any baseline %'s would have to fluctuate depending on what market you are looking to accomplish this in.

Yes sir, as you know this fluctuates but in ideal scenario its about 20%.

That area can be tricky to judge because it has nicer areas and then a block later on the same street it has pretty run down areas, and because of that the rents and demand seem to fluctuate a lot depending mostly on the base.

The reason you see dramatic value fluctuation because Detroit is a hard market to analyze and takes some walking around.

Since rent rates can fluctuate greatly, and appear to be over inflated in my area at this time I would love to take into consideration average rent rates rather than just the inflated rate landlords are getting right now. 

It's definitely still a sellers market here despite the fluctuating mortgage rates as inventory is really low.

My loan officer tells me payment calcs should be left to him due to rate fluctuations and nuances in taxes across different locations.Is it too much to ask my loan officer and real estate agent to provide an estimated payment and rent amounts up front?

As someone who has invested in equities my whole life I was trained to look at the WACC value or Beta of risk based on the fluctuation of similar equities.

WL is a more steady growth where the IUL has more fluctuation in the returns. 

Lenders will consider 75% of the rents towards your debt to income ratio.Personally, I try not to bank on appreciation because markets fluctuate.