I might be wrong, but I think you basically need a broker at least to close the deal. You will be able to save some money in broker fees since you are already bringing in the buyer, but I think that TLC requires someone with a TLC broker's license to close the deal.
This is done primarily to protect the parties involved. When the amounts involved become such large sums for the sellers, and many of the buyers are making their first major investment in America, it ensures an honest transaction. Also, the broker puts together a lot of the paperwork that is requried to close the deal, stuff that you might or might not know is involved, and without it the deal goes south. Usually, the broker's fees are like what ??? 2000 if you bring in your own buyer, so on a 525k purchase, this is peanuts. Besides, what they usually want is the insurance business afterwards, and to be able to line up the loan. Insurance is insurance, usually all the prices are about the same. Loans are generally close, but it helps to check out Bayridge Federal and Lomto before going with the broker- sometimes you can get a better deal after the Legal Fees are thrown in. Legal fees don't exist with Bayridge and might not with Lomto, but Pearland I know squeezes you hard.
One thing that you should do on your own and should never pay a broker is to form a corporation to buy your individual medallion. Pay the $150 or so online at the NYS Dept of State, but don't pay the brokers $595 to do the exact same thing. That is just a rip-off. And when you do buy your individual medallion, make sure you buy it through a corporation. It is simply foolish to do otherwise.
Good Luck,
Antolin