What are the requirements for a holster when carrying a concealed weapon in Florida?

Forget about the holster unless you have a permit for carrying a concealed weapon. Luckily for you and me Florida still allows it as long as you pass a background check. If you have the permit you can holster a weapon anyway you like! You are required to tell police that you are armed if pulled over or otherwise approached, and I would keep my hands above my head with fingers intertwined.

Whether or not a pistol is “accurate up to 20+ yards” is largely up to you, and what your standards for “accurate” happen to be. General rules of thumb: the bigger the pistol, the easier to hit with at long distances, but the harder to conceal; the smaller the pistol, the more difficult to make hits at long distances, but the easier it is to conceal. That said, both pistols* you mention are perfectly adequate for concealed carry, depending on where you plan to wear the hip holster, what kind it is, and how adequate the cover garment. Two general types of belt holsters: Inside-the-waistband holsters (IWB) are more concealable than outside-the-waistband holsters (OWB), as half or more of the IWB holster is worn inside the pants and disappears below the belt line. If you chose an IWB, those made of kydex or other material that does not mash closed when the pistol is not holstered are preferable to soft holsters that collapse when the pistol is drawn. They are preferable so that you may holster one-handed. OWB holsters are generally more comfortable than IWB, but less concealable. Where you wear the holster: A holster worn directly on the hip presents a fast and efficient draw, but may not prove as concealable under a t-shirt as one worn slightly behind the hip. If your hip is considered the 3 o'clock position, the small of your back 6 o'clock, you may find a more concealable, or comfortable position, somewhere in between. Many suggest avoiding the 6 o'clock position, however, in the event of a fall, which could prove injurious to your spine. Appendix carry, as suggested by another poster, is also a useful, but less popular, carry position. The cover garment: Consider length. Since you're going to wear a t-shirt, make sure that it keeps the firearm and holster concealed when you raise your arms above your head. This should help prevent accidental exposure in public. Consider weight. A t-shirt that is too thin will often show that you're carrying something underneath it (this is called “printing”). Consider color and pattern. Some colors are considered to print less readily than others. Generally, these are dark colors. Patterns on shirts are also considered helpful when it comes to avoiding printing. You won't really know what will work for you till you try out what you have. Some will prove acceptable to you, some not. The belt: Get a proper gun belt. Not one that will suffice. Not one that looks like it might work. Get one that was actually designed to carry the weight of a handgun. This one accessory alone will save you lots of pain and aggravation. Practice: This goes without saying. Having all of these things will not prove useful in an emergency if you don't practice drawing from your holster from beneath your t-shirt (and other cover garments). Practice safely, seek qualified instruction in your area, and good luck in your endeavors. * NOTE: The Glock 23 is .40 caliber, not the 9mm you say you are interested in. The Glock 19, however, is a 9mm, and is physically the same size as the Glock 23.

There IS no set standards for carrying a gun in a holster. You can just slip it between your belt and body, if that is what you want to do.