You can use several ways to transfer that old vinyl record collection to digital, from recording them as regular audio files to compressed MP3 files. The total digital storage they will occupy depends upon the quality you select. While there may be little difference between the sound you get from a WAV or AIFF file and the MP3 that you can hear, that really depends on how the MP3 is recorded.
An average long-playing record album is about 45 minutes of music. This can vary from about 30 minutes to 60 minutes for some, but the industry standard---so therefore the majority of your record collection---was 45 minutes. This provided the best audio quality, although people such as Elvis Costello decided to test it with his "Get Happy" LP and pushed it to nearly an hour. In standard digital audio, this is about 450 megabytes. This means you can get about an album and a half on any CD. This is why many recording artists first released classic albums on CD with bonus tracks. First, they could because they had the room, and second they wanted to fill up the extra time on the CDs. An example of this is David Bowie's 1972 LP "The Rise and Fall of Ziggy Stardust and the Spiders From Mars."
For a standard MP3, an album will take up about 45 MB of disc space. This means you can get about 10 standard LPs on one CD. However, you can get more digitized music on a compact disc if you lower the quality of the MP3 recording. The average MP3 recording quality is 192 kilobytes per second, but you also can record in 96 kbs, 112 kbs and 128 kbs for lower quality but more music per disc, or at a higher rate such as 256 kbs or 320 kbs for less compression and better quality.
With standard MP3 compression of 192 kbs, a four-minute song is approximately 5.5 MB. That means you will get a little more than 127 songs on a 700 MB CD. At 96 kbs, you will get double that or 254 songs per CD. If you use the higher-grade 320 kbs, you will get fewer than half the number of songs on a CD. Since most people can't hear the difference between a digital recording made in standard audio quality and an MP3 at 192 kbs, this may be the best way to digitize most record collections. However, if you want every nuance of a vinyl record in the recording, stick with standard audio.