HI Iff,
leave entitlement as well as the absences themselves can be configured completely independant from payroll.
If the same rules apply as for those on payroll, all you have to do is set the relevant groupings for this staff the same way as for payrolled staff. If not, separate them - probably best by groupings for employee (sub)groups rather than personnel (sub)areas, but that deoends on your setup - and configure absences and quotas in the same tables you used for payrolled staff just for different rules.
no problem whatsoever.
regards
SVen