Depends on what you want it for and how long you expect to need it, but purchase of a fireproof safe can be cost effective -- especially if you can pick one up used.
http://ezinearticles.com/?The-Benefits-of-Fireproof-Home-Safes&id=71384
". . .A fireproof home safe is an easy way to protect your most important documents and belongings in case of a home fire. A safe deposit box at your bank, however, is the safest way to store your important papers. But if you need more space or would just like to keep your important belongings at home, you need a fireproof home safe.
Most safes are fire-resistant, not fireproof. The fire-resistant safes are rated by the Underwriters Laboratories. They rate safes based on how long they can protect paper in a fire at different temperatures. Class-C fire-resistant safes will protect paper from a 1,700-degree fire for one hour, a class-B safe for two hours at 1,850-degrees, and a class-A for four hours at 2,000-degrees. You will need a specialized safe to protect computer documents like disks from fire.
Small fireproof safes start at around $50. These hold only a few hundred cubic inches and weigh less than 20 pounds. If you need more space, then you will need to spend more money. Larger fireproof home safes start at around $200, but can cost thousands. Fireproof safes that expensive are usually for guns or commercial use.
Many Internet retailers sell fireproof home safes, many at low wholesale prices, but you may have to pay for shipping. Try to see the safe in person before you buy it, since returning the safe will be expensive. Check out your local home security stores. Remember, you are putting your most important documents in the safe. Make sure it is the one you want. . . "
