I just refinanced my rentals at 3.99% on a 30yr Fixed with a 10yr I/O, so they do exist. 

An appraiser is trying to compare apples to apples and nothing else.

40 year amortization and 10 years i/o would have me salivating, depending on how good the rate is.Financing is a tool and it has to make sense with your overall business plan.

Apples and oranges. 

Again usually brokers hide their commission in "Lender Discount" for the rate chosen.Unless your dealing with a HELOC I/O where the rates are set a little different?

@Andrew Kiefer  I think your talking about apples and oranges when you ask about 2-4unit and 5+unit builds.

Hi Napat,Make sure you are comparing Apples to Apples.For instance is the Contractor going to use Owens Corning Synthetic Underlayment, or X mil plastic sheeting or tar paper, or nothing because he believes (for instance) hail damage is less with nothing under the shingles, and the Ownes Corning guy is going to use the Owens Corning Synthetic Underlayment (???)

so if i sell apple stock and make 15K in profit, would it be a wash?

(Repairs, Utilities, Insurance.....not mortgage, not capital expenditures)It is an easy way to create an apples to apples comparison of the risk involved in an asset and market.

Ensure that you're comparing apples to apples as well, meaning the properties you use for comparison's sake should not only be of a similar style, size, number of bedrooms and bathrooms but should also be in similar quality to the level you intend to remodel your rental.If you are working with an agent and are trying to buy on market, they should be able to help with this.