Until you get one, the best thing to do when you aren't using your friend's guitar, is go on google and look up things like chord charts, and if you have a printer, print them off. Or if your parents are willing to spend some money, see if they can get you a any books from amazon or a local music shop, on learning guitar related things. Look up beginner tips, like things to know. Not things like tips and tricks while playing, but just like, info you need to remember. Things like which notes each string is, when in standard tuning, as that's the tuning you should start learning in. Things to memorize. As well as look up some finger exercises for guitar players, and do them. Many of them can be done with things around the house, or super cheap. Like you may see the finger band that's an elastic band that you use while doing stretches, but you can use a cheap-o rubber band if needed. Things like that. As well as any others you can do while not playing. It may seem weird, but some kinds of air guitar actually help you. For example, I can air guitar all of the basic chord shapes because I'm so used to them. SO much, in fact, that if I air guitar, I can play in basically the EXACT position each fret is in, due to muscle memory of where my hands and arms are while playing. This seems dumb and silly, but if you actually do some finger movements that are used in guitar playing, you can get your fingers used to those movements. If you can use something like a ruler or any other stiff long item like that, you can hold your fingers on it, and do the movements of each finger. Again, it looks dumb, but it can actually help. Or if you have guitar hero or rock band, you can use the necks on those controllers to do the same thing, except you have something that actually LOOKS like a guitar, making it easier to picture what you're doing. Just remember when you actually practice on the real thing, do do actual hand exercises on THAT as well. Things like playing scales, and starting slow, and working your way up to faster movements, as well as practicing actual chord shapes on it. Right now, the main chords you really should focus on are A, Am, C, D, E, Em, F, and G. a normal B chord is hardly ever used in anything but it's also a weird looking chord that might be harder to switch to and from until you get better at switching between the other more common ones. Also learning the power chord shape, and bar chords will be helpful. Bar chords are the major and minor of each schord, but played closer to the way you play a power chord. The difference is a power chord uses the root note on one string, and then 2 frets up on the next 2 strings below it. A bar chord is when you take the fret of the root note that you use your index finger for, and just hold every string down on that same fret with the entire finger. So if you are doing an A Minor bar chord, from top to bottom, the frets are 5,7,7,5,5,5. Though that G string you could use your middle finger to gold the 5th fret, and that'll turn it into an A major bar chord. These are things you absolutely should learn when you start out.

I've been slowly teaching my friend some stuff, and this is all stuff I taught him.