That is also a crutch you do not need as an adult in business.

The Tenant agrees that the premises shall be occupied by no more than _2_ persons, _1 or 2_ of which are adults over 18 and _0 or 1_ of which are children under 18 years of age"

Considering that only 65% of Americans are homeowners...

I have done it all my adult life.  

Even in America, going by household income, 90% of USA households earn less than $150K a year -- 70% of American households earn less than $75K/yr. 

If nothing else with average americans its as @Mike H. pointed out.. it makes financial sense over renting.... especially in the example Mike provides..

This person is an expat (American English teacher) with an employment contract and a work visa for at least 1-year, which is the period of the lease.  

I am 59 years old and have had the bulk adult life in the construction business and I held a broker license for about 30 years even though I never did that full time.  

As a young adult, I began my own business socked away money for my future (though I saved for med school and had no idea I wanted to invest til later on).Since they are already college-age and have summer-only employment and are looking to invest in the near future, they either need to save money working more hours; forego instant-gratification luxuries (like dining out/new phones/new clothes); or wait a bit longer to invest.

http://finance.yahoo.com/news/86-american-renters-cant-afford-000000211.html