There are a lot of karoake songs floating around and quite cheap.. With a good Yamaha arranger you can make very decent back up tracks. I used to do it for singers here in NYC.
It depends on your tastes.. You might want to have the fun of playing your guitar, recording like the old days.
If you make them MIDI however.. you can custom change the key, tempo for various artists. If you use a DAW and record the chord Detect chords, you can change the whole style of the song very quickly.
A lot of the small clubs pay little to nothing for entertainment, the singers, artists are doing it for exposure and to be discovered. If you find some good clientele, with decent gigs, they will be willing to pay more to class, and something unique, 'their own sound, style'
Good luck with it.