Check out Fight Pass for a lot of the preliminary cards plus a mega library of past bouts. The UFC Fight Night cards are currently on the Fox Sports family of channels but will soon switch over to ESPN. They seem to have two or
three of those per month most of the time.
Usually, when they have a PPV event, it is delivered in
three stages. The early prelims will be seen only on Fight Pass, the main event prelims are shown on network TV, usually FS1 at this time (ESPN in the future), and the main card is PPV only. That usually includes three or four fights, including the actual main event. Hope that's not too confusing.
ETA: The next big fight is Nov. 3. Daniel Cormier vs. Derrick Lewis for the heavyweight title. I'm sure there will be several early fights on FS1 and fight pass that night.