Pay Per Posting Plan
From Smart Job Board help
Plan Description:
"Pay Per Posting" Membership Plan model can be used when you want to charge users for every job/resume they post on the site.
Subscriptions to such plans are usually free and unlimited, since users are only charged for adding postings. Total number of listings users allowed to post can be unlimited as well.
Also this type of the plan does not allow making Resume Search.
Setting Instructions:
1) Free Subscription:
Open the "Add a new Membership Plan" (if you're creating a new plan) or "Membership Plan Info" (if you're editing an existing plan) form.
To make the subscriptions to the plan free for users you need to enter 'zero' or leave it emtpy to the "Subscription Price" field of the "Add New Membership Plan" form: 
2) To make the subscription to a plan unlimited you need to enter 'zero' to the "Expiration Period" field or leave the field empty:

3) Users pay per each job/resume posting
On the page with Package settings to the "Single Posting Price" field you need to enter the price users will be charged to post 1 listing (e.g. 5$):

4) You'll need to specify the expiration period for listings users will post (e.g. 15 days)
For that you need to enter 15 to the "Listing Lifetime (days)" field:
5) Users can post unlimited number of listings.
Open "Manage Plan Permissions" page, find the "Job Permissions" section (if you want to allow users posting Jobs, otherwise set "Resume Permissions", or both)
There you need to find "Post Job" setting.
- Check "Allow" box to allow users of this Plan to post jobs.
- Enter '0' to the "Number of postings" field or leave it empty - to allow users post unlimited number of jobs: 
Note: Set the rest Plan Permissions according to your own discretion.

