I read the article but couldn't quite figure out what George was saying. I understand what you mean by demos. I wrote them, graded them, and advised others and was part of the chain.
You are right that "owner occupy predominance" is the "generally accepted" palabre for why you don't rely or develop the income approach for SFR's. Say that, and you will pass muster in perpetuity. In a demo, you are just showing you can develop it and make the normal "sensible" comment and thus show a professional capable of"due diligence."
But what does reality say? I use other principles, not in most appraisal texts.
Postive versus normative - Positive is concluding what the indicate. Normative means concluding how it ought to be, opining what is "normal" in absence of data. Appraisers do both. Post a thread about how much to adjust for a house painted pink, and someone will hit you that adjustments MUST come from the market. But you are going to have to best-guess, PFA, SOPE it, because the market will never give you that data. I put this right in my scope-of-work disclosure - how much of narrowing the range is the data, and how much is my guesstimate.
Inference versus simulation - Appraisers do both. Inference is saying these babies sell for $100/sf so subject is worth $100/sf. You are not walking in the footsteps of the buyer. You are not saying the buyer say, 'ooh another square foot, I am going to pay another $100.' It's a simple and primitive matter of statistical correlation. For example, if you use regression, a critic will hit you for a lack of simulation - 'buyer's don't use regression." But $100/sf is what they pay, predicting prices is the name of the game. On the hand, you could try to "simulate" the market, by doing what buyers do. That would include using the type of residual method that someone like McDonalds might use for land value or building value. However, you will find because of collinearity (Austin's favorite word) that even McD's has figured out a shortcut, all they have to do is count the cars. That leads to the next principle
Shortcuts - Most appraisals and some methods are shortcuts. Just about any inferential method is a shortcut. If they sell for $100/sf, then that's what they sell for and I dont' have to engage in the teduim of walking in the footsteps of the buyer. You were posting elsewhere about DCF and direct cap, but the fact is that direct cap is just a shortcut. You don't have to account for future value, changes in income stream and gaps in income stream, you just assume they are the same (perhaps not stating all these stability assumptions and forecasts, just saying, these babies sell at 9% cap rates).
Least variance and collinearity - This is why a little regression concept helps. Most appraisers will say that if one unit of comparison makes a tight range and the other makes a wide range, the first better explains the market. But this idea of least variance is not dilligently and rigorously applied. Collinearily, on the other hand, means that if you have similar properties, the price per anything is going to make a similar range. This is why "the three approaches" do not accurately or adequately break practice into its logical components. Price per square foot, or per doorknob, or per light fixture are one approach, but price per dollar of income (GIM to appraisers) is another, separate "approach?" Mathmatically, its the same approach based on a diferent property attribute. Price per dollar of cost is another separate approach? Well, if price per doorknob, or per light fixture don't really "confirm" price per square foot, then why does price per dollar of income confirm it as a "separate" approach?
Generally speaking, positive beats normative (comps rule), inference beats simulation (comps rule), and least vairance wins (that is, comps indicate 100-110 beats comps indicate 30-200).
Let's apply this to a real life case study - and go back to your comment about the income approach and the owner-occupied matra, while applying the above principles.
Many years ago, I appraised condo units in a small, diverse market. Some projects had hundres of units, some as few as 12. The local population is relatively transient, so there is probably a high number of rentals, anyway more than enough for income cap.
I found based on three years of sales, that the GRM's formed an amazing narrow range. I think two standard deviations was something like 118-132. This included local and resort properties (which included some units in short term rental plans), all improvement ages, all amenity packages, and everything from studio to 3-bed (least variance). These properties were not "investments," so even though this "inferential" method did not "simulate" what buyers did, it was highly price predictive. It was completely "positive" (exactly what the data indicate) with no appraiser "norming" (what some would mis-lable as "subjectivity"). And yes, it was a great "shortcut" to the problems of direct sales comparison. Apparently, the market saw the proportional quality among these properties as the same, whether they were going to live there for one year or several years (collinearity), and nothing gets around time adjustments better than this months market rent and this months multiplier.
Most assignments did not afford the oppurtunity to use "comps" from the same project. After all, if there are only twelve units, the last sale might be five years old (and what if the 12 units had different floor plans). To avoid time adjustments, most appraisers used comps from other projects with adjustments that had to be "normative." Sometimes, especially on the 2-bed and 3-bed units, which sold more rarely and showed greater project differences, appraisers would develop battle fatigue. (That's why I stopped appraising churches). I reviewed on assignment where the appraiser included a long narrative analysis and reconcilation based on three sales from three different projects. In one way, it was masterpiece. However, battle fatigue probably caused the appraiser to fail to notice that the abutting unit with the same floor plan and level of upgrade (all original) was listed for $25,000 less than the final conclusion of value. Ouch!
These appraisals and reviews brought three typical reactions: 1) very clever (rarely), 2) you must be insane (much more often) and 3) thanks for the appraisal, but I really thought it would have come in higher (most often). I can remember one conversation with the senior loan god at a big bank. He said it was hard to believe how low the value is. I said, there are two things. First, that's exactly what the data indicated that day, and second, about five days after the appraisal, one of those units sold for within $1,000 of my appraisal. After a pause he asked, is there any way you can appraise this for the higher number (the original loan value) so I don't have to book the loss in this quarter?
So, an income approach can be the "best method" for residential property, even if only in the rare circumstances, I described. I doubt it would ever have that little variance in SFR appraising.
-----
Using my "theory" we now unravel several sets of problems that further disconnect cost from market value. It's not just that at square one, cost isn't value, and cost might not even be "cost." The cost approach itself as promulgated by the AI, is a "simulation" method. As that course said, the buyer says why should I pay you $200,000 when I can build one for the same amount and get the same or better benefits. I'll avoid the math problems on this here, to point out that this premise holds that the buyer knows land values, and the cost to construct. But in real life, few do. That is, the cost approach to market value attempts to simulate buyers, but these actions are something buyers don't do. Thus, the process of doing depreciation is inherently "normative" and it is going to lose to sales comparison on the basis of postive-normative and least variance EVERY TIME. That's why there is no sense in developing it.
So, some appraiser takes one million in cost and "simulating" a process no one uses, "norms" that into $700k, and then there is bunch of comps at $850k (or the appraiser "backed in" to $850). Either way who cares? I would
never rely on an appraisal for market value based on the alleged "cost" of the subject.