ZombieLenin -- and kcdusk -- has covered it all pretty well (and welcome to the forum both of you).
I'd add that it's worth a look at DriveThruRPG and browse the Twilight:2000 material because they usually have some sort of bundle deal going on if you ever want to buy more. More importantly, they also have some "guides" to the earlier editions that'll give you a better idea of the product range and what it offers.
http://rpg.drivethrustuff.com/index.php?cPath=23
As for can it be played with just two people, like ZombieLenin said, yeah sure but I'd suggest having an NPC that is lower rank than the Player's character. While the Player will be telling this NPC what to do, the Referee works like an overseer and makes sure the Player doesn't abuse the situation (for example, making the NPC do all the dangerous work, or give up all their gear and so on).
Always keep in mind that it's post-apocalypse and although combat is a big feature, the game is also about long term survival and the eventual rebuilding of civilization. You don't have to have your one and only Player trying to fight off hordes of badguys every adventure. Think about what would be interesting in a survivalist sense and make scenarios that give the Player a decent chance to use brains or stealth and not just firepower. That is to say, make adventures that allow the Player more than one way to complete the task.
**EDIT** And the whole reason for creating this NPC is something I forgot to mention. It gives the PC a friendly face in a hostile land, someone who can watch their back, help fight off the badguys, someone who can talk about "back home" with them and also someone to look after the PC if/when they get wounded. Keep in mind the PC "should" consider doing the same things for the NPC.
It also gives the Referee/Game Master a way to add additional information/advice/skills to the game so things won't automatically go bad if the PC doesn't happen to have the Observation skill for example or the Player just can't figure out a good plan of attack (the Referee can have the NPC 'make a suggestion' kind of thing).
If you're having trouble thinking of suitable adventures, check out the following links for some ideas: -
http://www222.pair.com/sjohn/blueroom/plots.htm
http://www.rpglibrary.org/articles/s...ng/36plots.php
http://www.gnomestew.com/tools-for-g...f-plot-design/
You said you only have one friend interested at the moment. That's all you need to start. Explore the game together, have a few test runs and when you both feel happy with the rules and the gameplay, check the net or your local game store to see if there are others in your area interested in the game and organize a social get together to discuss your interests and plans for the game.
That's pretty much how I started and some of the people I meet at that time are still in my circle of friends twenty years later.
And don't be discouraged if the first (or even the second) group you meet up with doesn't 'click' for you, different people have different ideas on how they want their games and it really can be a case of trial and error.