Hi Vudak,
Simply put, its fraudulent and its wrong for more reasons than I can list without writing another book, and I'm too tired to write another book.
Its an attempt to defraud the US Government and ultimately the tax payers (that would be you and me) in time of war. The housing allowances are there to help the legitimately married couples live off base and raise their children, they are generous partly because the military recognizes that the family finances are the last thing a soldier needs to be worrying about in a fire-fight. Additionally, around here the budgets for things like guns and armor and training are already tight, so the idea of paying for fake marriages would make the blood of a lot of commanders boil - and that won't help much when your budy is getting charged.
Additionally, he is entering into a legally binding marriage contract with someone with demonstrably bad financial skills and a penchant for doing questionable things to solve them which could make him eventually liable for alimony and/or child support for many years to come, and believe me "But your honor, we only got married to defraud the government" isn't going to be a solid gold defense in divorce court.
So to sum up:
It's Immoral
It's Illegal
It's not particularly bright
It can ruin his career
It puts him in a VERY vulnerable legal position
They will probably eventually get caught
Heck, its even unpatriotic
Tell the lady in question to sell off anything that she doesn't need, and then to get a job and some credit counseling, alternatively she could try getting married
for real to someone with a solid income and a reasonably pleasant demeanor. But wait, I guess that kind of thing is outmoded...