Why not run it as a gestalt game rather than a single-class campaign? Do you know gestalt rules?
Really, the trouble with a one-person game is you're going to find most challenges are WAY over your head. You'll need to take measures to make him more powerful if you want to run an Adventure Path, for instance, because Adventure Paths are balanced around groups of 4 players. Keep that in mind.
That said:
1) Gestalt characters with high point buy are what you want. Assume 25 point buy. Between the two of you, you SHOULD be roughly comparable to a 3 person party. Ignore the combinations it lists, however; those are only somewhat applicable to Pathfinder and even then the designers of the book didn't include Cleric/Wizard as a combination and that's a VERY powerful combination.
Basically, Gestalt lets you shove the best qualities of two classes together, but you still have the action economy and hit points of a character with only one class.
2) Include Hero Points in your game so you have a bit more of an edge.
3) Give yourself a bit of extra gold to start the game - say, 500 gold - so you can get somewhat better equipment.
4) Run an adventure path. Go in knowing you may very well (and probably will) die. Play smart, play safe, and let your roommate (the one who's not the GM) make the major decisions.
I'm a fairly new DM that just started and had a group go from two to one. It can be rough at times, but definitely still rewarding all the same. There are plenty of free level one modules on the site you could try out to get your feet wet. Remember, though, that his druid will have some decent strengths. Roll stats and give him a free 18. Make sure he picks a strong animal companion to increase his survivability. DEFINITELY give him a little extra gold to start -- maybe even a free masterwork upgrade to his weapon if you feel he needs it.
If you're going to run a module/ap first, as stated above, know that you might have to scale it back a bit if you're not going to gestalt him. (I wouldn't personally recommend gestalt since you're both new to this, but still). Just don't be afraid to kill him and DEFINITELY don't be afraid to make mistakes. Its going to happen.
Have fun.
Fortunately, a Druid is a great class to solo with since it gets an animal companion and can cast SNA spontaneously.
Druid is one of the top choices for a single player campaign. They have a great deal of versatility themselves and an animal companion. They are one of the most self-sufficient classes out there, and would be especially powerful any any sort of outdoor/nature themed setting.
However, any character will fail a save on a 1, and some failed saves mean you lose. Having friends there is a huge insurance against that problem. There isn't an easy solution to that.
In general, I find that a solo character can usually handle encounters that are designed for characters 2-3 level lower, so if you want to run an adventure for 1st level characters, a third or forth level character can probably make it, unless they get unlucky.
Mostly though, just try it out. Relax about being 'prefect' and have some fun.
(I wouldn't personally recommend gestalt since you're both new to this, but still)
This is something to keep in mind. Gestalt is complicated for people just starting off. If you think you understand the rules, though, it's an option.
If you're unsure about your understanding of the rules, don't do gestalt.
A druid + an animal companion + high point buy + a second party member + higher starting gold should give you a good boost that will help you survive. This is doubly true if your second character gets an animal companion in some form as well (ranger, cavalier, paladin, cleric with the animal domain).
You can also let him simply play an entire group. I've done this on occassion and while it's a lot of bookkeeping for the player, it tends to be safer. The player can approach it by adopting the role of each character when needed (for non combat stuff) or by just picking one as the "leader" that handles all of that and the others are treated sort of as NPCs.
This provides ready-made characters for any players you find that want to try the game out prior to committing to their own character to replace one. If you go this route, the classes with pets or summons become less mandatory. This would work best with APs as well. If you are running a custom campaign it's far more in your control to design something suitable for a signle player.
You could give his main character a re-worked Leadership feat at 1st level. Maybe he's a important personage from somewhere and travels with three bodyguards. But that is ultimately just masking the above solution.