2nd floor studio? Why not!
My studio is on the second floor of my house.
So far I've only had two issues with that; 1) my gear is upstairs, and 2) low end rumble while mic'ing
1) My gear is upstairs.
On a daily basis this is a non issue. However, if I'm loading up for a gig, or merely want to host a jam session/cook out, I have to disassemble the set up, and drag stuff down to the garage as it's the biggest open area in my house. While that's not the most fun thing to do, it's nothing compared to bringing the stuff back UP the stairs, especially if we're talking about the guitar and bass cabinets at 100 pounds each.
2) Low end
rumble.
I have a double floor in my house that consists of the plywood subfloor, a 1' gap for the joists, a layer of drywall, another set of joists, and another layer of drywall which is the ceiling for the first floor. The house was origianlly a single story, and the family that owned the place before I did added the second floor. In any case this layering affect has created roughly 5,000 cubic feet of acoustic chamber.
The problem with this is that when I've recorded my drum kit (
Sonor Force 3001 5pc) the kick drum goes BOOM! It hits like a canon which is great for jamming, but way too much for recording. It's easy enough to fix with a prodigiuos use of low cut/High Pass Filters on the mics, but it is something to deal with. Not unsurmountable and easy to fix, but you have to be aware of it.
Over all, EVERY ROOM will have it's issues, even if it was designed by an acoustition. You just have to figure out what those issues are, and figure out how to deal with them. I'm recording acoustic drums and live bass, so for my purposes this can become a problem, but if all your doing is your voice and an acoustic guitar, or an electric through a simulator and
EZDrummer loops, you'll have minimal issues with this.
I say just go for it and have fun creating the best music you can. Don't wait around for things to be perfect like I used to do. Just get moving on it and have fun!
