The general rule for outbound diallers seems to be that you need a minimum team size of 8 - 10 agents and a minimum list size of around 10K records per month to allow the dialler to work effectively. So even using a hosted pay as you go solution may not work for a team size of 4.
In terms of using a hosted solution, I have previously used this solution for an in-house outbound telemarketing team of between 8 -12 agents. We were able to load and dial multiple lists and obtain excellent Management Information. There were occasions when the dialler went down so we couldn't call, which was frustrating but this can happen when you have your own dialler. The benefit was that we had dialler management and technical expertise available through the hosted solution so we didn't need to employ our own technical people and saved on headcount.
Hope this helps.