In the world of fiction writing, there's nothing more exciting than taking a character on an adventure through a world of mystery and imagination. However, sometimes we want that world to be our world, and while the character might be fictitious, we want the world to be familiar. At this point, parts of reality creep in on our storytelling, and we should keep this part pretty accurate. Now we need more than just a creative mind - we need information.
Get researching. During the past decade or so, there have been tons of books written about the housing crisis and the subsequent collapse, as well as a few good movies (and, of course, movies based on those books). One quick trip to the local library or a few minutes with Google should be able to hook you into a few good sources for background information and context. I am sure there is even a "The Great Recession for Dummies" out there, though I've never checked. The point is, get yourself enough information to at least establish a working knowledge for your character. You don't need to become an expert, but at the very least you need to clear up any unknowns you might recognize before you start writing.
Get help. A lot of people have their own war stories from the Great Recession, and plenty of people are willing to share them. This is one of the few good uses of social media - finding different pages and gathering different experiences. If you have a rough idea of what your character's particular role should be within the banking community, target stories that focus on this. There is absolutely no shame in saying, "I'm writing about the housing crisis and want to know what a good role would be for a character who caused some of the problem then tried to fix it - help!" Plenty of people will be glad to offer ideas - just take a pause to make sure the responses are coming from experience rather than political bias or just plain anger.
Get vague. Needless to say, the underlying financial mechanisms that set off the financial-market crisis are pretty complex. You might not understand them, and your reader might not either. This is where you need to take inventory and decide how detailed the story should be. In these cases, less is more - step around the nitty-gritty of the situation and emphasize how this person is engaging with the story. If the character gave out a lot of mortgages to people with bad credit records and troubled finances, the reader doesn't need to know just how bad the credit scores were, what rates were charges, the terms of the mortgage, etc. They just need to know that this character was bad news. Now, if the character was a mortgage trader, this is a little more complex and might require a little jargon thrown in. And if the character worked with default spreads, swaps and leveraged trades, your ability to be vague is limited indeed.
Working with the details can be a tricky task, and sometimes it's better to work with the character's motives, attitude, and approach to the situation. Ultimately, it is our job to show a character as a good/bad person. If we can do this without detailed demonstration, then all the better. However, a little legwork into the subject matter can parley into a lot of information.