As you would expect in a place with the nickname of Motor City, car rental in Detroit is quite common and surprisingly easy (as long as you work with a well-known car rental company). If you are traveling to Detroit in the near future, you should strongly consider renting a car: it will really enhance your experience while you are visiting the city.
Because Detroit is a major city, all of the large car rental companies have car rental locations throughout Detroit. I could give you recommendations about whether you should choose Hertz or Avis and what car you should rent, but it really comes down to personal preference and your specific situation. For example, I normally rent a different car when I’m alone in Detroit on a business trip than I rent when I’m in Detroit with my family on a vacation. The best piece of advice I can give you is to compare the prices at some of the major car rental companies (such as Budget, Avis, Hertz, etc) on a car that you are comfortable driving and then select the company that best fits your budget.