The best cheap bed frame really depends on what your definition of cheap is. For some, it is best to choose a low-quality unit that may not be usable for long-term purposes. In other cases, a buyer may want an inexpensive unit that will still stand up to regular use for many years. Your budget will generally determine which units are appropriate for you. When choosing a cheap bed frame, try to find one that is sturdy and safe, above all. Make sure you buy a frame that is appropriate for your size mattress, too; smaller frames will usually be less expensive than larger ones.
Inexpensive, collapsible steel frames are perhaps the least expensive option. This type of cheap bed frame will feature metal slats that connect together; these slats are then suspended by either casters or legs, thereby raising the box spring and mattress off the ground. Such frames are usually fairly durable, though they are not always the sturdiest option and are perhaps the least attractive option. A buyer on a tight budget should probably consider this cheap bed frame option before any others.
If you are willing to spend a bit more to get a cheap bed frame that is reasonably attractive as well, some types of platform bed frames can be quite inexpensive. Look for frames made from softwoods such as pine. Softwoods are generally far less expensive than hardwoods and they are often just as attractive, but softwoods do come with their own sets of disadvantages. First off, softwoods tend to be far less durable and more susceptible to warping, chipping, cracking, and rotting. Bug infestations are also more likely on softwoods than on hardwoods. In most cases, softwoods will need to be painted or otherwise sealed to help prevent water damage such as rot.
Of course, you can also build your own cheap bed frame fairly easily if you have some carpentry skills. Buying some lumber from a lumberyard, or using reclaimed wood can keep the cost of the unit down, though you will need tools such as a circular saw and drill to create the frame. Pine boards can usually be purchased fairly inexpensively, and a low bed frame can be made from pine boards and even plywood. It is best, however, to avoid placing a mattress directly onto the plywood; instead, coat the plywood with some sort of waterproof sheeting.