The ARV is the final price that the house flipper is going to sell the property for, someday.From that number we need to subtract out all the costs associated with the deal.

Does this exemption amount get subtracted from the sale price of the property, or the assessed value of the property? 

You also want to subtract the repairs from the already discounted price. 

including your labor, it was a value subtract. 

I want to ensure that I'm covering myself safely for Capital Expenditures; but are not some of these situations, not all but some, covered by the home warranty and with that do you subtract that amount of coverage from what I should budget for each month for Capex?

Subtract RE taxes and insurance and maintenance if you are going to calculate a net return.Appreciation is only realized after a sale not while it’s only on paper.

If I subtract 15K for rehab, that leaves 20K.

My forecast is that it likely will perform worse than as an LTR after subtracting for a PM.  

They say I will be guaranteed rent each month minus any expenses they subtract out no matter if it is rented or no.

Even if you were to do an annual tax appeal, the price at which you purchased won't necessarily be a big factor; a recent appraisal or recently sold comparables will be used.Your annual water number sounds very low.You omitted trash and sewer.You omitted rental license and inspection.I don't think you'll want to spend $200 on advertising, given that there are lots of free internet sites that you can use.Just because there are houses asking for $1250 in rents does not mean that they are seeing that number; sometimes they over-ask so that they get the maximum possible when Section 8 takes the voucher amount and subtracts utilities; Norristown 3 bedroom vouchers are netting landlords ~ 950 depending.