A few years ago the easy answer would have been to pickup an older Volkswagen Bus, but those things inexplicably cost more than many new cars, so we'll skip to something under the $10k limit. This 2003 Ford F-350 Super Duty Crew Cab pickup here on eBay for $8,900 buy-it-now offers ample seating for 6 and a huge rear cargo section for drums/instruments. Slap a Bob's Pest Control sticker on the side if you want to people to leave it alone. It could almost pass as an Animal Control vehicle -- maybe put a "danger, may contain live snakes" sticker on the back.
What can you guys find that is a better band hauler? Comments below.