Yeah, boiling water straight from the kettle should kill most bacteria. Also make sure the net dries out properly, this will kill anything like ICH which needs water to survive.
the above suggestions are great, but to be safe, i would buy another net. they are not too expensive and you won't be risking disease spreading to your other fish.
Hmm, well if you buy a new one every time it will add up. The boiling one works great, just soak it in boiling hot water and dry it with a paper towel or sun dry it.