Lumberjake93 said:
mandolin and harmonica... excellent for playing... perfect.
Harmonica is the perfect instrument. They're cheap, portable, and harmonica players have the best pulmonary function of any group of people, better than horn players, opera singers, marathon runners, or breath-hold divers. I know harmonica players in their 80's and 90's, and they all attribute their longevity to harmonica playing.
Another great instrument is the spoons. They're cheap, easy to play, and easy to carry with you. For drummers who don't have a massive van, learn the washboard, you can play with drum sticks. Hand percussion is great, things like tambourine, cabasa, djembe drum. My newest instrument is the jawbone of an ass. Really, I'm not kidding.
look here
Guitars are great, but they're a little bulky and good ones are sensitive to changes in temperature. There are several ways to deal with it. One can just get a cheap guitar, or get a
Composite Acoustics Cargo , the perfect guitar for a cargo van. Or, one can take up the ukulele. Ukulele is much easier to play than guitar, they're cheap and don't take up much room.
Ok, I'm going to tell you people about the greatest festival you'll ever find. It's called the Ukulele World Congress. It's a free festival, the camping is free, there is free food most of the time, and there is FREE BEER the whole time. People come from all over the world, Australia, England, Germany. It's in Indiana, they aren't trying to promote it because it keeps growing every year and they don't want it to get out of hand. I do a harmonica workshop there, it's free of course.
The best $100 I ever spent was for my Yamaha electric keyboard. It does everything, runs on batteries, and packs up nice to fit in the van. I have a friend who lives in an older, smaller van full time and he has an electric keyboard set up in his van.
Just to brag a little, I have a Bose PA system, a deep cycle battery and a 300 watt full sine wave inverter. I built a cabinet that has 4 wireless mics and a Bose "audio engine" (mixing board). I can open the back door of my van, turn on a couple of switches, and have a wireless guitar, wireless mics for vocal and harmonica. I don't play in a band at the moment, which means I'm available!