Since you are not studying to be an appraiser, please let us know why this question is relevant to what you're doing. We don't do appraisals.

What Candice A. Donofrio says.

Being sure you're getting ALL of the accurate numbers from the owner is probably the biggest challenge.

it's not a difficult task... you must have the correct income figures....

We would not appraise, but a commercial broker WOULD analyze and evaluate and provide an OPINION of value.

And it's not really hard at all when you know how.

However, the biggest challenge is going to be making sure you have ALL the expenses right so your NOI is accurate. From there out, it's formulaic. 

Still, even for a commercial property, you'd use more than just income to determine value.

I have no idea... I don't appraise. I am not a licensed appraiser. I suggest you refer this question to an appraiser.

Start with having a good timber inventory and know the timber markets in the area...

on the other hand, unless you are becoming a commercial appraiser or investor, you will never need to deal with this.

Dunno, never done it.

Determining rental value from advertisements, rental survey from management companies and Craigs List rentals is pretty variable to find the market rents fora residential appraisal. Cost approach is more valuable

Realtors don't do appraisals.

The cost to build and how much rent one can obtain differs from locations

Mike,

This is something that an appraiser can answer.  In commercial real estate, we did a "rough" pro forma for our clients for their accountant to review and rewrite.  This was to explore what could be earned on a building whether it was an office building or a retail development.  Again, this was not a certified report, it was for discussion only. A

Finding rental comps.

The most difficult part of the market data method of appraising is adjusting for differences in the properties

FIrst having all the data, all the income and all the exenses. Most come to me with much missing. Then once you have it all, knowing how to calculate it

Never use it. 

I have no idea.

I don't have the knowledge or experience to answer your question since I have no need to make those judgments and I am not an appraiser.

I wish you all the best with your real estate studies. 

Finding and adjusting the comps.

Not hard if you have a good P & L on the property. If you have good income numbers determine the rate of return you want and offer a number that generates the income you want. Obviously you have to factor in the condition of the property and adjust accordingly.

Getting the details of operating costs.

I do a CMA, not an appraisal.

Sorry, I can't help - I'm not a licensed appraiser.

Verifying the income and expense numbers!