One economical way to create an additional room, such as a bedroom, for a limited period of time (for example, until your eldest goes to college), is to install temporary walls or sound-proofed partitions that can be removed easily when the time comes that it is no longer needed. A perfect example would be the case of two teenagers who share a room. When they reach the age at which they want more privacy, install a temporary wall or sound-proofed partition. Then remove it when they move out. The room then requires very little work to convert it back to a bedroom. This can also be a solution if you are looking farther down the road to a need for a living space for aging parents after your children have moved out. Rather than build a wall that creates two smaller rooms, the temporary solution meets the immediate need and is easy to remove to create a long-term solution to a later need.

{google7280636161}

If you found this tip helpful, you might also want to read this:
Reallocate existing unused or under-utilized space instead of adding on
Finish your basement
Finish your attic