Not a stage owner, but I've set up quite a few over the years.
Homebuilt is an option, but these tend to be even heavier and bulkier
than commercial stages. Having a commercial stage gives you a load
rating and maybe some liability coverage.
Thinner stage decks are lighter, and fine for a panel of people
speaking, but are more bouncy and can sound more like drums.
Thicker decks absorb more sound, better for bands. 3/4" minimum, 1" is
better.
Plywood is strong. MDF fiberboard is strong enough, absorbs more sound,
and is heavier.
A felt carpet pad and a carpet can significantly reduce the drum noise.
Decks with honeycomb cores can be a good option:
https://se.stageright.com/wp-content/uploads/sites/4/2015/09/stageright-all…
Individual 4'x6' decks are lighter than 4x8 decks, but the total package
can be a bit heavier since there are more legs and framing.
Some stage legs are adjustable for setting up outdoors on uneven ground.
Shimming with plywood under the legs may be an option.
16" height is good for regular dances and smaller festivals.
I know one custom stage a festival uses that is 21" high.
Bigger events get taller stages.
Over 8" high you want solid steps, with a handrail, that attach securely
to the deck.
A 12'x16' deck will store in a space about 3'x4'x8'.
Get the velcro skirt.
Two strong people can manage 4x8 stage sections.
Use hand-trucks and dollys to move sections from place to place.
Two experienced people can have a 12x16 stage together in 1/2hr.
An in-experienced crew of three might take an hour.
Folding legs setup faster than installing legs, but may not be height-
adjustable.
Time to transport includes driving, maybe 15 minutes to load and
un-load, plus extra for stairs, elevators, long distances from storage
to truck/van, weather considerations, etc.
Speaking logistically, a lot of audio setup can only happen after the
stage is completely, safely set up.
What other organizations would you feel comfortable sharing the stage
with? Don't rent to a harley biker party!
Maintenance is mostly just keeping the stage clean.
Do NOT let anybody put staples in your stage!
Clean beer spills right away.
My guess is rentals are expensive because many stages don't go out that
often. And few people want to store, move, set/strike.
Or somebody comes in and wants a stage that's bigger than you have, or
they need it to be taller. Or...
Thanks and good health, Weogo