One of the POC FDs I am a member of just built the Denver Drill prop shown on youtube by Dale G. Pekel. Members here also built a forcible entry door prop. I built a restricted passage prop from a sheet of plywood and four 2x4s. My other POC FD bought the lumber to build a vertical roof vent prop that will also have a wire entanglement hazard prop underneath.
The only limitation is imagination.
At FDCQ,we bought large training facilities with budget of local government.For those small training pros like a wooden trench training for comfined space rescue,we DIY.The training pros are more on the training purpose,meaning we buy or make the pros depends on what we wanna train with.If we want a swift rescue,we probably hire hundreds of workers to dig a swimming pool near the firehouse.
I've found some great ideas in the books and resources from FireServiceBooks.com