Commission Income - New job, same industry

According to the Fannie Mae Selling Guide:

"A minimum history of 2 years of commission income is recommended; however, commission income that has been received for 12 to 24 months may be considered as acceptable income, as long as there are positive factors to reasonably offset the shorter income history."

I have a (potential) borrower who is looking to relocate and obtain a similar job in the same industry that is mostly commission-based. Does the borrower have to wait 12-24 months before his new commission is eligible toward qualifying, or can it be counted right away since it's in the same industry? My guess is that he has to wait. From an underwriter's standpoint, I'm thinking it is hard to predict what his level of income would be because it's a different employer and a different market. However, I believe there are a number of underwriters that frequent this forum so I thought I would double check.