There are a range of support options available for open source software, many of them free. The open source community tends to be passionate about its technology, and there is an ethos of helping and sharing. So you'll find numerous forums and communities dedicated to the support of open source projects.
And the answers are easy to find. Search any help question for an open source product, and you'll most likely find a forum post with the answer. Forums members are quick to respond to requests, too. Want paid support? You'll likely find it for a lower fee than for the official support of commercial software.
Open source projects often have no fee attached, and this non-commerciality tends to be an important part of the open source community's ethos. Furthermore, consider the lack of an expensive upgrade push and the availability of free or affordable support, and the proposition seems even more attractive. Often, you receive functionality equal to or better than that of commercial software, and significant value-adding extras, too, for no fee whatsoever.
While not every open source project is better than the commercial competition, it will frequently give it a run for the money. You get better security, with quicker bug fixes. And the slowly changing nature of open source means your business won't be forced to adapt to new upgrades every year. Support is responsive and accessible, and the products are eminently affordable. All this means you should consider your open source options whenever acquiring new software.