they don't tell you this in school, but you can order a mattress from an online retailer and "return" it.
because every online mattress store is a shitty drop shipper - they don't take actually take returns, so they ask you to destroy the mattress or donate it to a charity (no charity actually accepts used mattresses). just fake some documentation saying you brought it to the dump and waluigi you have a free mattress.
real image from a real email that may or may not have gotten into my inbox somehow. that or SWIM got it in their inbox. i obviously would never do anything illegal ever.