Acting as a buyer's agent is tough as you are considered an autobroker and there is a ton of state level laws around this kind of business. Some of them are extremely archaic, but are kept in places by an extremely powerful lobby organization.
If you are interested look up the battle TrueCar became embroiled in recently because of some decisions they made in their business model. The end result was they lost over half their paying dealer network and half their revenue in a matter of a couple of weeks. They were disallowed from operating in a dozen or more states over night.
They have recently had to completely change their product to come into compliance. Their aint no lobby like an auto industry lobby! :)
It's a very complicated industry to move into successfully. We have done a good job (IMO) of navigating the mine field while offering a compelling service to Consumers and Dealers.