A lot of the other duplexes and triplexes in the area have shingles and a lot of them have metal roofs so as far as getting renters neither one will really deter anyone.

Because the risk is lower (because the borrower met all the guidelines), the rate and cost is lower.The next level would be portfolio lenders. 

Unless the surface is a factory finish or a baked on metal type finish.

I work as a welder metal fabricator 9-5 and my wife is a sales associate.

If all you have is a masonry facade over a fireplace unit, which is what it sounds like if you have a metal flue, like for a gas water heater or furnace, it should be an easier removal.

Plaster, in my neck of the woods and target properties, is always plaster-on-lathe, usually wood, very occasionally metal.

I personally know a friend of mine who called his insurance company and they paid for a metal roof, they had no damage but the adjuster said there were few damages on the shingles( he had shingle roof).

Example, we stopped buying barstools that have nuts and bolts to tighten and switched to a single piece metal design.

They don't look to be that much further away from where you are putting in the metal ones.

I sold a house one time to a rehabber where the previous owner stripped the home and sold everything including the metal roof!