You haven't said exactly what you would be buying it for but I would jump on it and here's why. Low or no down, seller financing and low or no interest with a balloon payment later is the holy grail (location, building condition, market also matter but it sounds like you have all that). You could trim your expenses by eliminating property management - you can absolutely do this yourself on a 6-unit, even as a newbie. I'd be surprised if the complex doesn't have individually metered units so you may be able to eliminate the utility expenses unless those are for common areas like walk ways, parking lot or laundry. Each tenant should be paying their own utilities. Even if you don't decide to keep it in the long run, it's an appreciating asset you can make money off of. If he doesn't need the cash now, you could also negotiate a split you're comfortable with to get him the return you and he feel he should have at the point you refi when the balloon payment comes due.
