Any system that 'allows' homes to be sold to people on income too low to afford this in a conventional manner is a mirror of EXACTLY what happened and got us into the mortgage mess. It was the government that decreed to the lenders that they had to meet a certain quota of loans made to the 'disadvantaged' in order to get funds from the government thru Fannie Mae and Freddie Mac. This was the creation of the 'sub-prime' and Alt-A mortages and look what has happened.
These are the cold hard facts. Check it out.
Government, the same people who are still in charge - congress, were the ones who caused this mess by their interference in something they knew and still do no know anything about.
If you can't afford it, then should not be able to purchase it until you can.