In since-deleted comments, OP specifies Michigan and alludes to a particular location. I am familiar with "dangerous Michigan locations".
First, I'm going to make a broad, inclusive statement about all Michigan cities with 600,000 or more population.
They "all" look like donuts economically, with depressed inner cities, but very robust suburbs.
People in those suburbs tend to repeat a prejudiced cliché: that the city is full of crime. They really believe it; many Suburbanites wouldn't be caught dead in them. And yes, there is a racial undertone to that cliché.
What's actually true is that the city is a madcap checkerboard of middle-class, affluent and desperately poor blocks, and this varies almost block by block. It's like 3 blocks of San Francisco, 4 blocks of Ann Arbor, 5 blocks of Flint, and 2 blocks of Love Canal.
What's also true is that the city has bottomed out and is recovering, including fixing a lot of corporate/structural problems like owning a money-losing utility that was still generating DC power for street lighting. Now, all the cool kids want to live there, at least the nicer parts of the checkerboard, and the words "gentrification" are starting to be spoken.
And so you have to scope out your destination literally block by block to determine the level of threat. Keep in mind if the business you are servicing is there, it may be in one of the good parts, at least by day.
You should also be mindful of hours/time-of-day; some places are safe only during normal business hours. 10am may be fine; 8pm not so much.
Now, as far as guns and Tai Chi, very large Michigan cities have gun control, so check with your gun lawyer and know your RoE. But far more important, guns are not an "I win" button! They require genuine skill and experience to use effectively, or at least, more effectively than the other guy. The same can be said of both Karate and Tai Chi.
And with Karate particularly, the problem is Karate is an external martial art, where force meets force, and force is emphasized - while it can help, it depends heavily on inflicting techniques on the other person, using strength to do it, and if he's much stronger, you have a problem. Tai Chi has real potential as an internal martial art, with all the right bits to be extremely effective in survival street fighting. It can make differences in strength irrelevant. However it is extremely difficult to find a teacher who teaches Tai Chi as a martial art. Doing the arm-waving Yoga dance without having experienced e.g. "wipe hands" as an effective way to pry off a stronger attacker's grip, is just mistraining yourself. You must understand and practice the martial aspects, on mats, tossing people all over the place, with falls (another thing to learn). This takes thousands of hours and cannot be done for a work assignment.