Were members of a posse reimbursed for their time and expenses, or was their service voluntary?
Payment depended on the government body involved, but, for the most part, these amateur lawmen were volunteers who had to provide their own horses, guns and so forth. If a reward was paid for apprehension of the subject, the sheriff or marshal would usually share it with his possemen.
Not all of these townsfolk were rawhide-tough frontiersmen, as is often depicted in Westerns. They often faced hardened criminals who would do anything to avoid capture. Still, quite a number of these possemen died bravely in the line of duty.