Sterilize a bed or a couch?

Not easily, no. That's why hospitals keep mattresses covered in waterproof covers. You can certainly have them cleaned professionally, of course- but that's not the same thing as sterile. It does however, remove the most worrisome things from the equation. Then you can simply keep a mattress cover on the bed. Personally, I would want the place visited by an exterminator first and have it all treated for critters. The bacteria isn't the problem, really. It's the livestock you need to watch out for.

see if you can get the rug doctor from jewel/osco. You rent it out for a day or two and I think it is like 25-30 dollars. Ask behind the customer service counter or i think it is photo counter. And you can get it steamed clean. It will remove all the dirt and grim and there is a certain non abrasive shampo that comes with it. It would be a lot cheaper than gettting it professionaly clean. I have used it on my couch before. Also sometimes you can take off the cover of the couch seat pillow if there is a zipper or way to get it off and put it in the washing machine on delicate. I have done that as well.