Really going to depend on the location traffic. I'd say if you had 1 pin in a brew pub, you might make $40 a month the first month. Split that with the location you made $20. By the end of the year you might make $10 a month after the split.
Figure you're going to be replacing coil stops, flipper buttons, balls, cleaning, etc. So figure parts and time. Then a ball gets stuck, someone put a Canadian quarter through and jammed up the coin mechs. So now the game has been off for 2 weeks. You just made $5 that month.
If you average even $25/mo after the split its going to take 200 months or 16.5 years to pay off the game.
Good luck.