The biggest pro is obvious: cost. DJ software (Rekordbox, Serato, VirtualDJ) can be expensive, and hardware is a massive investment. Being able to download "crates" of music for free allows a bedroom DJ to start mixing immediately without a recurring subscription to a record pool.
Downloading "ripped" music from paid pools (stealing music) puts you at risk of malware from shady file-hosting sites. Furthermore, if you plan to stream your sets (Twitch, Mixcloud, YouTube), using pirated music can result in your stream being muted or your account banned. dj crates free
When using free DJ crates, keep in mind: The biggest pro is obvious: cost