The statement of the claim in the question is extremely misleading, and the article confuses multiple projects. However, the Red Cross housing projects are receiving scrutiny from investigative news organizations
TLDR: The article has accidentally or deliberately confused the earthquake relief project with the much smaller neighbourhood renewal project, and attacked them both for not doing things they weren't intended to do. The Red Cross did much more in Haiti than build six houses, but it may not have been as much as could be expected
Let's focus solely on the specific claim in the question, that "all the Red Cross did with half a billion dollars was build six houses".
Other parts of the article raise some possibly valid concerns about the Red Cross effort in Haiti, which have been noted by other reports, and are to some extent shared by many of the organizations operating in Haiti, but that particular accusation is not one of them.
Specifically one of the things the article is doing is confusing two entirely different Red Cross programmes - the earthquake relief programme and the LAMIKA project. The $500 million figure they quote is all about disaster relief. It is probable that the reference to 130,000 promised homes is also a reference to the earthquake relief work, although I haven't been able to track that down.
In the article, one of the key points is:
After the earthquake, Red Cross CEO Gail McGovern unveiled ambitious plans to “develop brand-new communities.” None has ever been built.
There is a link to a press interview with Gail McGovern, supposedly backing this statement up. The interview does not contain the quote, nor any similar statement. We have to dig around to find out whether there were indeed such plans. It turns out that at a press conference in 2011 McGovern did in fact announce plans for "a hundred million dollar program to provide permanent housing in Haiti". Several schemes seem to be included in these plans, one of which was the LAMIKA project, which does have the goal of "neighbourhood renewal", and is referred to in the article. However, to be completely clear, it isn't directly funded by the earthquake relief budget and doesn't have a $500m budget. Lamika appears to have a budget of around $9.5m.
Regarding what the Red Cross has actually done, the article says the following:
The Red Cross says it has provided homes to more than 130,000 people. But the actual number of permanent homes the group has built in all of Haiti: six.
Note the clever insertion of the word 'permanent' in the refutation, but not in the claim. In other words the Red Cross never claimed they had built permanent homes, but the article is taking them to task for not doing so. In fact the Red Cross has never listed 'permanent housing' in its priorities for the $500m relief fund. The earthquake relief fund's focus (or one of them) is on temporary housing.
The Gail McGovern interview contains a statement of the Red Cross priorities for earthquake relief in Haiti:
McGovern oversaw a six-pronged strategy in rebuilding Haiti that encompassed improving food, water and sanitation; building emergency shelters; jump-starting livelihoods through jobs and grants; strengthening health services and establishing future disaster preparedness.
There is also a summary of the Red Cross' actions in Haiti:
In Haiti, the Red Cross gave $30 million to the United Nations food program; spent $14 million on readymade meals, clean water and latrines; provided more than one third of the country's tarps; gave more than 1 million vaccinations; provided loans and cash grants to catalyze business development; and trained hundreds of thousands on how to prepare for the next potential disaster.
Note the mention of 'emergency shelters', and of 'tarps', which are key components of temporary housing.
Where the confusions starts is that the article also makes reference to "Lamika", speaking as though it were part of the $500m earthquake relief work. However Lamika is in an entirely separate project from the Earthquake Relief work. It is about renewing the Campeche neighbourhood near Port Au Prince. Lamika does not have a $500m budget but a $9.5m budget.
It is not clear what happened to the Red Cross plans to provide permanent housing. Current statements of the LAMIKA priorities say that it is specifically about building neighbourhood infrastructure i.e. the things that go around the houses. Priorities in the Lamika project include roads, schools, water and sanitation, public spaces, and "Reinforce or expand more than 300 houses" (i.e. repair existing houses, not build new ones) However reputable news organizations such as NPR are also asking questions about why the permanent housing plans have come to nothing, and about what has happened to the earthquake relief money.