if you are serious concerning this, i would suggest you start with a single floor installation of walls. Use 2x3 wood to make the frames and pallets or 1x3 for the walls, or plywood. No need to board both sides of the walls.
In doing so, you can quickly attain a 4-5 room + corridors construction that will resemble a 4 1/2 apartment or first floor house.
Then Roam the city you live in and check in alleys and stuff for old junk like chairs, sofa, tables. take anything you can and stuff it in your 'kill house'.
Charge a mere 10$ per entry to your field and invest 100% of that money into your field. In a year, with about 10-15 players, you'll have a village setup with at least 5 installations. That way you can make MOUT and CQB at the same time.
Be sure that you are gonna need at least 500$ worth of investment to start your constructions.
Hope this helps.