Just so that you know, owning a pistol is useless without the knowledge and the conditioning to use it. As for additional expenses, you're looking at:

-- Defensive pistol courses, often at $600-$1,000 a pop, plus travel and lodging, in addition to ammunition, extra magazines, etc. This is a perishable skill, so if you cannot find ways to maintain it (and it's often hard to maintain it, because ranges often do not allow anything but standard target shooting for safety reasons), you will have to retake these courses regularly.

-- A new wardrobe, so you can carry concealed. You will have to get larger pants (usually two sizes larger), plus jackets, shirts, etc. to help prevent the print through.

-- Naturally, there is a whole range of accessories, starting with a good concealed holster.

-- I'd also recommend some sort close-quarter combat training, or at least weapon-retention training, so someone can't disarm you easily.

You can get a decent compact gun for $500, suitable for concealed carry. But there are many other things to consider. There are generally administrative expenses, assuming you live in a state that allows concealed carry. If you want to carry in more than one state, you may have to get a non-resident license from Utah or Florida, which is a non-trivial recurring expense.

You may also need to consider a backup gun. If you have a semi-automatic for the ease of use and the higher capacity, you might want a more mechanically robust "six for sure" revolver than works even when not entirely clean.

You will also have to change your behavior patterns. There will be some places that you may not be able to to go without your gun. So you will have to figure out where to deposit your gun while you go there. You may not hug people anymore. You may lose friends. You may scare colleagues. You will have to learn all about gun laws. There are many people in jail who had thought they were justified in self-defense, and the jurors disagreed with them.

So don't just run out and buy a gun, unless you are willing to make yourself informed, trained, and well-equipped.

Da Bing