A futon is simply a wood frame futon or metal frame futon, which holds a mattress. A futon design is based on the old Japanese practice of rolling out of bed and sleeping on bed mats, which were stored away during the day. The futon is a convertible piece of furniture that works great in small spaces, like lofts. During the day the futon frame is folded (angled) up to form a sofa or chair and at night the futon frame is straightened to form a bed. It's this multiple use and space saving design that makes the futon ideal for smaller rooms and apartments or places which may not have distinct living and sleeping space. It is comprised of a futon mattress, futon frame and futon cover of which there is a wide variety for each.
Although this type of bed is very convenient and efficient for those requiring more space throughout the day, they are not as comfortable and do not provide as much support as a normal bed and mattress would. These types are generally designed as guest beds and individuals who would be sleeping on them on a temporary basis only.
If you do choose to use a futon as your daily sleeping bed, there are things you can do to make it more comfortable so it provides more support for your body (especially your back). You can buy extra thick futon mattresses that are designed to give you extra support for your neck and back. You can also purchase mattress pads, which will provide extra support and better quality sleep. When using this type of bed permanently, make sure to buy pillows that are designed to offer support to your neck and back.
Overall, futons are great beds that provide convenience and efficiency for individuals who cannot afford elegant beds and who need extra space throughout the day. The cost will depend highly on the size, make and design of the futon. The more you are willing to spend, the better quality futon you will receive. You will benefit from spending a few more dollars now, rather than have your futon broken within a couple of months.