This allows me to consider more than just a score (which can fluctuate between agencies) and it is not a hard credit inquiry.

(20% or even 25% makes the numbers much more appealing for the cash outlay)Are 20 year ARM loans the standard or do some lenders offer longer amortization periods and rates that fluctuate less on these kinds of deals?

From my side of this (as an architect), we can estimate what a project will cost, although it can be off by quite a bit as construction costs can fluctuate greatly in a years time.

You don't want your income figures to fluctuate based on when tenants pay rent.

I know current rates will fluctuate based on the actual date of closing, but I would like to figure out required downpayments, structuring of PMI(For FHA), mortgage fees, and how move in ready does the property have to be in order to receive financing(Ex: some Freddie/Fannie based loans are strict on only lending to houses that are move in ready).

If these numbers don't fluctuate from the mean , then $18,000  -  $20,000  will be a likely amount in real Cash $ that I can expect to receive each time that I go to do a Cash-Out refi. on a property ? 

The break even for conventional versus FHA I would say is safely found around 680 - 700 fico since at that level of credit score the mortgage insurance for Conventional starts to become less expensive, however this fluctuates because you should look at the total effective rate between the loan and the mortgage insurance on an apples to apples basis.If FHA is at 3.50% but monthly MI is .85% your effective rate is 4.375% "all in," but the problem is FHA has a Up Front Mortgage Insurance Premium - UFMIP - of  1.75% (points) thats added to your loan as well and this is harder to factor but a good way to put it on par with conventional is to raise the rate to a level where you can payoff the ufmip or absorb it in the rate.

The difference between the payment and what the payment should be as result of rate fluctuation is added to the principal.

I don't know about your state but I thought a deadline of April'ish was pretty common.Your escrow amount can become short due to fluctuations in the actual cost of taxes/insurance and also because they have to have 1 or 2 months reserve of that newly increased amount also.I would try to raise rents as much as you possibly could if you're past the deadline for protest this year.

So there is a lot of fluctuation.