IMPORTANT: you need a high-quality 4-inch razor scraper, not the cheapest on sale.

Its about the right size / type / condition for the property I would like to find to upgrade from the duplex I sold in 2019,   and from my research,  it is likely that the ownership are getting to the point in their tenure where selling might be on their minds.Given the building's likely income/expense numbers  (I own a nearby, similar style/quality property I can extrapolate from) I can make an educated guess to its value and given that value range I can afford it without excess leverage.   

It seems that the greatest factor in the quality of the deal is not the cost to acquire the property but the rent on the units. 

Dwelling (Building coverage)The limit should be based on the Replacement Cost of the building (cost to rebuild withthe same kind and quality excluding the foundation)2.

@Christopher Dolan ultimately that decision is up to you, but I would start by conducting a survey of all other rentals on the market and figure out where your rental fits in based on condition, quality and location. 

Even the nice ones are of lower quality and there is a stigma attached to them.Other than that, it's difficult to answer the question without knowing your market.

But to counter my own point, a lot of customer decision comes from location, your interior design choices, reputation and photo quality.

If the shed adds value compared to other homes of comparable location, quality, and size, then I would bump the rent $50 - $100 depending on the price of comparably storage units in the area.

With a commercial property, @David Beasley, the lender cares much more about he quality of the deal and your experience as an operator.

@John Redman the LL responsibility for the quality of drinking water varies by state.