Guys how do I make an incomplete measure at the start of a song? Say I want to make the first measure have only 1 beat, and then at the end of the song make up for it with a measure that is 3 beats long. Thanks for any help 
When you mix down, just select from the 3rd beat of the first bar to the 3rd best of the last bar.
I don’t think there is a way to set the timeline to start on beat 3. I think it’s good to have 1 or 2 bars of silence at the beginning when your tracking and mixing anyway. If you start on beat 1 of the first bar, some plugins mess up. Good to give them a little space to initialise etc.
Good advice to not start at zero on the timeline. I’ve actually found myself writing intro parts of several bars long after the fact that I start my songs on bar 50 as a matter of course now.
BTW - would starting the song with a single bar of 1/1 time signature work? Or the first bar being 5/4 (assuming the rest of the song is in 4/4)?