Dale, it is certainly going to need some kind of retention.

Otherwise it is going to fall out when you take off running because the zombies are closing in on you, and you are carrying a 9mm. And well, lets be realistic, the same scenario could play out if you run across a pissed off squirrel in your yard.

Only slightly more seriously . . .

Drop holster - the purpose is to keep the pistol readily accessible while carrying a battle rifle and wearing body armor. Drop holsters - that I am aware of - all feature some form of active retention.

Gun games - high on the belt line, grip of the pistol is held out away from the body, "retention" is also important but not as . . . robust, as one would want in a less controlled type environment.

Your private property - depends on what you are doing. That is one of the few (in my opinion) places the $8.00 Uncle Mikes nylon holster with a velcro strap type holster is applicable and appropriate - in most cases. Now if you are doing tree work for instance, climbing 60-80 feet to top a tree . . . that $8.00 holster may not be the right choice . . . .