When we had a baby on the way, my wife evicted all of my music gear so we could set up a nursery. Then, as a Father's Day gift, she got me one of those 10x12 wooden yard buildings. We insulated and sheetrocked the interior; her father, an electrical contractor, put in all the plugs and light boxes; and I finished it off with carpet, air conditioning, and a ceiling fan. It's a really sweet place to work. There's enough stuff in it to take care of any weird bounces in the vocals, and I record my guitar stuff direct, anyway, so I haven't run into any problems. It's been a real blessing.
Small studio tip -- Get yourself a Mesa/Boogie DC-5 combo amp. It has a direct recording output that sounds exactly like the cabinet, plus there's a switch on the back to turn off the speaker, so you can get as loud as you want, crank the power tubes to the max, and nobody needs to hear you. That, and a digital drum kit and you are really cooking!