If you are going to pay per ticket you have to take into the thought:
1. How many tickets per day
2. Where your help is going to be based from. (USA/UK will cost more than India such as BobCares.com)
3. Is one person going to be able to handle all the tickets to make a decent amount of money.
4. The hours you want them to answer the tickets.
We do offer this service for a couple of different companies (not just hosting) and just answer the questions right long with our support questions. We require a base of $50/month + $1.00 a ticket. Now this is only for pre-sales and general help. This is not a to troubleshoot cgi's and teach people how to build website. Straight Hosting support.