What the typical music library size for a non-comm or LPFM station?
The music library size depends on the format.
If your format is divided into different shows with different styles, then there is no way to attach a number.
If you are doing classical, you will want at least one orchestra's version of every work, and with the most well known, several at least.
If you are doing CHR, you will not do anything different than a commercial station... about 15 to 20 currents, maybe 60 to 80 recurrents.
Anything else is in between.
If you describe the general format, we can give you "hard evidence" based on playlists of commercial stations on library size. As a non-commercial station, you may want to extend the reach of the library... but remember that the size of commercial station libraries is determined by asking listeners what they want to hear.
So if songs are not played on commercial stations, there are two reasons: first, the song is disliked, and, second, the song does not fit a mass appeal format.
That means that you are likely to want a format that is not available otherwise. That means getting a good cross section of representative and well known songs, periodically adding new releases and, maybe, resting some in cycles.
The principle cautionary note is: don't think your taste is the same as that of your potential listeners. The last time I tried to "guess" how listeners felt about songs I was wrong by 20% or more on about 75% of the songs (and that was with a #1 radio station when it did its first research)!
If you give us a general idea of the format, I think you'll get quite a good perspective. Remember, programming is part art so there is no clear "right" or "wrong" way. There are many alternatives in playlist size, the rotation (frequency of play) of different songs and other details.