Hey so I have a acoustic 12 string and the very first string of the bass line, going down, is broken. The thing is I can't afford a new set and I was wondering if I can use a string from a normal 6 string acoustic. Or if that would hurt the guitar. And if so which string would I use? Thanks
More than likely, that very lowest string on the guitar is the same gauge as the bottom E on a standard acoustic guitar. Its gauge will be around .044-.046" ish. So, yes, by all means get just a bottom string.
If it's the octave of that E - the thinner of the two bottom strings, again, yes. But here you'll need to use a D string - which will have a gauge of around .022-.028".
Best bet would be to take the broken string along to the shop with you - they should have a gauge to check the string thickness, or just by looking, get a good match. It's always a good thing to have a spare set of strings with the guitar, rather than waiting till you need a string or two.Sooner or later they're going to need changing, so if they're already there, you can carry on playing sooner!