Further comments from question:
A contract marriage is defined as a business agreement where you share the same roof, you are married for name sake; but it is only for the military benefits.
As far as I can see, the Bible says nothing about contract marriage. The Bible treats marriage as a union of a man and a woman before God (not as a civil contract before the state). See particularly Matthew 19:4-6.
Essentially a contract marriage is not a marriage, in a biblical sense, but an arrangement to take advantage of whatever benefits acrue to married couples. There seem to be two problems with such an arrangement. One, it seems, at least on the face of things, to be inherently deceptive. When a country legislates to provide benefits to married couples the intention is that those benefits should go to people who are in a geniune marriage. For example, a contract marriage to the purpose of getting higher military pay is not a real marriage but a pretense for financial gain. Arranging a fake marriage is essentially an act of fraud.
A second problem with a contract marriage is it seems to degrade marriage. The Bible says marriage should be held in honour (Hebrews 13:4). A pretend marriage or a just-on-paper marriage does not seem to honour marriage. It seems to make a shame of marriage.