Should I accept the used mattress my neighbor is offering me?

My next door neighbor of 16+ years is moving. While helping him move some stuff to his new place, I mentioned that I haven’t been sleeping well for a while and he decided to come over and take a look at my mattress. He thought it was in terrible shape, and now that I think about it, I’ve had this mattress for an extremely long time (I’m thinking maybe longer than I’ve been neighbors with this guy!). There’s a big indentation in the center (which perfectly matches up with my butt or my gut, take your pick).

In any case, he offered to give me his queen-size mattress. I’m tired of sleeping on a twin-size, so I thought I might find a queen-size frame for cheap on Craigslist. The only question is: is it icky to sleep on a used mattress?

The neighbor is relatively clean; no pets or smoking in that apartment, as far as I can tell. I’m not sure if the mattress was used by him or his mother, but does it really matter?

I was thinking I could vacuum it, wipe it down, spray it with Lysol and maybe get one of those hypoallergenic plastic covers which are supposed to suffocate dust mites once the mattress is covered.

And of course, I should mention that I probably wouldn’t be considering taking the mattress if finances weren’t a concern. If I don’t take this mattress, it’s probably going to be a long time before I can afford to buy even a cheap new one for myself.

So: take a possibly icky mattress and maybe sleep better, or keep my old one for a few more years?