I have had clients on Welfare who called themselves "Middle Class" and I have seen multi-Millionaires call themselves "Middle Class". To be "Middle Class" has since WWII, been the place to be, you are not "poor" and you are NOT "Rich". The problem is defining "Poor" "Rich", "Middle Class" and the almost disregarded term "Working Class".
The person you responded to did address that issue. With Median Income around $50,000 half of the population earns less then that and half more (People who earn $1 million dollars a year are NOT included, to include such people pushes up the Median to much). Roughly 90% of the population will earn between $20,000 and $ 80,000 a year.
http://upload.wikimedia.org/wikipedia/commons/thumb/6/66/Income-curve-%2About 6% of the population earns more then $150,000 per year, less then 16 % earns more then $100,000.
Slightly more then 30% of the population earns less then $25,000 a year, Slightly more then 8.5% of the population earns less then $10,000 a year.
With those numbers we can have a rough I idea of what is "Poor" and "Rich". About 10% of the population tends to be on Welfare or receiving some sort of Government Assistance do to being poor. The US Government has determined that you need $674 a month ($8088 Dollars a year) to survive. If we accept that figure as "poor" then under 8.5% of the population is "Poor" (i.e. those earning less then $8088 a year). The difference between $50,000 and $9000 is $41,000 (I am rounding up for easier calculations). If we add $41,000 to $50,000 we come to %91,000 which leaves about 15% of the population earning more then that figure and thus "Rich".
Now under pre-WWII use of the term "Middle Class" that would be the groups just under the Rich, but then the term rich was reserved to the top 5%, thus in pre-WWII days that would be the people earning between $90,000 and $150,000 today or about 10% of the population (Which also happens to be the traditional percentage of the "Middle Class" to the people as a whole).
The problem is since WWII, we have been told we are all "Middle Class", even the 10% of the population that are "Poor". Thus has lead to a tendency to lower the numbers for both the "Rich" and "Middle Class".
Now, in the 1970s, a poll was done that showed most people called themselves "Middle Class" but if you added in the term "Working Class" to such a poll, it split the "Middle Class" results in half (I.e. 5% Called themselves Rich 5% called themselves poor, about 45% of the Population called themselves "Middle Class" and about 45% called themselves "Working Class"). These numbers seems to hold in polling but not in relativity, to few people call themselves "Poor" among other major errors including no definition of the terms used in the Poll except as to what class you belong in (I have NOT heard of any results since the 1970s).
The Federal Government has also had a problem with these numbers, for example anyone under $50,000 is "Low Income" when it comes to Federal Housing Assistance (and I will NOT go into the Low-Low Income and Low-Low-Low Income definition adopted in 1974 so to make sure Public Housing Agencies rent to people on Welfare instead of keeping them out of Public Housing, which had been the norm before 1974).
Thus if we use pre-WWII definitions, 75% of the population are "Working Class" i.e. excluding the 10% who were poor and the 5% who were rich and the 10% who were "Middle Class". This seems to be the best way to look at the numbers but it is NOT as popular definition as it should be.
If we use the pre-WWII Definitions then the Middle Class can be the source of the Cash to provide such fundings. They are making $90,000 to $150,000. You can borrow (When banks were doing their jobs correctly) up to about 20 times you annual income or roughly 2 to 3 million. Thus they have the money to support such a loan.
If you are calling people who are earning less then $90,000 "Middle Class" instead of "Working Class" then the numbers are NOT as nice. The prices tend to be beyond the top end "Working Class" parent can provide (And way beyond what lower end "Working Class" parents can provide).
Thus my point is that the key is how you define "Middle Class" not if the "Middle Class" can do this or not.