Can there be any cheaper way to exercise than hiking? Yes hiking on trails where there are no fees for parking and minimal cost to drive. The challenge to some hiking is that is is several hours drive to get to a good parking spot such as some of the areas near Dinkey Creek. The other challenge is that some of the hiking areas are in national parks which can have some significant admission fees. Yes, if you are a frequent hiker there you can save money by purchasing an annual pass. The great thing about those are they are typically good at many other national parks. Unfortunately they get costly. If you are a senior citizen, disabled, or a former USFS employee you may be able to get a discounted pass, but the cost still hits your pocket book.
Fortunately there are many options that are close and have no fee for parking or entrance. These include Fresno Sugar Pine Trail, Old Town Trail, Railroad Trail, Kaweah Trail and Woodward Park trails which are all right inside Clovis or Fresno city limits or county islands surrounded by Clovis or Fresno. The drawback is that these trails are fairly sunny so while they are great in the morning, winter season, fall season, and spring season they get awful during the summer summer season. The other drawback is since they are in the city going there isn't much of a get away.
If you want a close get away think about the Millerton Lake Recreation area. There is a multitude of trails and if you look you can get free parking. Buck Ridge Hoop and the Bridge Trail are also great trails each about 2.5 miles and free to use.