Will this work for a vocal booth?

I am looking at puting an isolation booth (guitar and vocals) in the corner of one room. 1. I thought about puting it in the closet because of all the crazy angles (it is the under part of stairs) 2. i would like to keep the room open for drums, or other potential 3. I don't have a big budget ($200-$500 depending on the value . . . ie: how much difference it will make). 4. The main purpose is for recording voice and acoustic guitars dimensions, pictures, and floor plans are located http://redstuffrecords.com/studio/ Your suggestions will be treated as gold. Will this work? I might not double wall it. Sound proof is not an object. Just good acoustics.

ps: I won't do any mixing here, just recording some vocals and acoustic guitar probably.

Good acoustics in that size means dead. Price insulation in your area for cost estimating. Andre