If you have not established the proper relationship with them or they don't have anything to authenticate or verify you yet, an email is not worth anything.

It sounds a little bit like you might be conflating "Subject To" with a land contract ... which is where you and the seller sign a contract in which you agree to take some forms of title, while the seller keep the deed, liens, and insurance in place until the conditions of the contract are complete.In either case, the two cases you need to be worried about are:1) The bank calls the mortgage note because they realize that you transferred the deed, which is within their right, as per their contract with the previous owner.2) The seller dies, having told not one other person that the two of you are participating in a land contract, and you have to provide the contract and proof of it's authenticity to the probate court/judge/lawyer/whoever to make sure that your contract is enforced. 

I just got a closing costs quote from TD bank: ~5200Origination 840Appraisal 525Credit Report 9Customer Authentication Report .85 (85 cents)Flood Determination 5Tax Service Fee 58Title Services and Lender Title Insurance 1470Owner Title Insurance 650Government Recording Charges 715Transfer Taxes 600Initial Escrow 240Daily Int Charges 90Homeowner's Ins 75I'm not sure how much less these numbers differ in Michigan.

The vacation rentals are usually for those bargain hunters or those who would like a more authentic experience.

TD Bank Closing Costs 1/16/2014 Philly, PA SFHGeneral Fees:TD Origination Fee 843.15Appraisal Fee 525Credit Report 8.37Customer Authentication Report .85 (cents)Flood Determination 5Tax Related Service Fee 58Title Services and lender's title insurance 1470Owner's Title Insurance 650Government Recording Fees 715Transfer Tax 600Items Paid in Advance:Initial Escrow Deposit 239.18Daily Interest 89.38Homeowner's Insurance 75 (Hazard Insurance)Total $5222.68

I've also seen a ton of auction web sites (and have also read up on how to tell the authenticity between them).

People who are simply more authentic in their day to day activities because they seem to not be burdened by alement of regularity. 

Can I call to verify it's authenticity?

At what point is it better to give concessions to get someone in vs when is the concession become to costly.Pending the authenticity of the numbers and the exact market it looks like a strong deal.

Therefore,  I think it's better to be authentic and avoid scripts.