If you're collecting a secured debt, you probably need legal help. You shouldn't try to repossess a car, for instance, unless you fully understand the law in this area. Hiring a reputable and bonded repo company is one option. Another is to hire an attorney and use the courts. Likewise, if you're trying to foreclose on a mortgage, you'll need the expert assistance of an attorney.
You can turn over an unsecured debt to a collection agency, which normally asks for 30 to 50 percent of the collected debt and expenses. But, if you are owed a lot and you believe the debt is collectible, hire an attorney.