Good thread idea! All GREAT info here so far..
At Netherworld, we have a combo of everything. We make a lot of our own costumes but altered thrift store pieces have been a staple since our beginnings. Our Icon characters are all custom-made.
We hire first, then costume to fit if we have time, but that's usually not a luxury that most haunts have.
I'll buy some things in bulk, coveralls for example if I know I need a lot and buy a big range of sizes. Depends on the show's storyline & characters. We've had actors from dwarf-size to 7'2" and from XS-10XL, so yeah.. it's always good to have a HUGE range of sizes available if you can.
Other things factor in like special needs actors, and any costumes used for stunts, like flying rigs or sliders..
Most of our actors in the actual show use their own pants & shoes, but over the years, we've supplied these pieces to create a better whole look. it all depends on what is seen by the customer. The ones that work the outside lines are dressed head to toe.
Our show is in Atlanta, & not air-conditioned, which means we still have very hot & humid nights when we open in Sept & in early Oct. so that factors in as well.
I have a lot of sleeveless gowns & tank-tops & often the chainsaw guys go shirtless,(in body makeup) but I also have to keep warmer stock for when the temps start dipping drastically at the end of Oct., so we do a lot of accessorizing.