For land which isn't being used for crops or animals there are temporary or permanent options available to you. Today let's discuss camping.
Other sites I have visited have gone almost exclusively to camping. When I've been at these places, I always try and chat with the owners, as they are a wealth of untapped information. Asking questions from someone who has been there and done it, can give you advance warning of potential pitfalls which may occur whilst setting it up. People love to talk if you give them the opportunity to do so. They can give you the ins and outs and what worked for them and what didn't.
You will need toilet facilities, although to start with these could be rented. Portable toilets, such as those seen at music events could be hired. I have a problem with this idea however. If you are planning on committing yourself to having a campsite spending money renting is never a good idea in my book. Also people don't like using these and may not return to your farm because of these.
**One note I would like to make here is if these are merely used as a temporary measure, people are more amenable. For example if you were providing a field for camping next to Woodstock or another large musical event which only occurs yearly.
Other than port-a-potties you will need to construct restroom facilities. If you are going to promote 'green or eco-camping' you may want to opt for a composting toilet.
If you or your spouse aren't adept at plumbing and electrics, now is your chance to network and barter. What skills do you have which someone is looking for? Use these as a way to get the work completed much cheaper.
Most campsites also have a sink area for washing dishes. If this is placed near your shower block there will be less plumbing to contend with. This doesn't have to be like a showroom, just useable and easy to clean. Think about the campsites you've been to.
Whether you decide to use well water, or mains water will be determined by your area. Where I live we use only well water. Showers can be coin operated units if you want to recoup some of the costs of water and electricity for heating the water.
Installing electrical connections on your campground. If you plan to allow caravans and not only those camping with tents, you should consider installing electrical outlets and dedicated parking bays.
One campsite I went to in the south of England divided his area into two. The caravans and RV's veered off to the right near the back of his farmhouse, and were supplied with electrical hook ups. Those camping with tents and others who didn't require these point were directed to the left field. Of course those with connections paid much more per night but this kept the area confined so would have cost less to set up initially.
Remember planning for plumbing and electrical points beforehand can save you headaches in the long run.
Now you have your dedicated areas for campers and RV's where are the customers?
It's a good question. You will need to advertise. For this you can go the traditional route of a sign on the main road if you are allowed by your local authority. Don't stop there though. A website with photos of people using your services should also be built. Don't panic if you don't have any design skills, many of the websites can be built easily. However there are sites such as O'desk and Fiverr where you can hire skilled people to construct a site if you feel it is beyond your skill set. A basic site is all you need to start with. This will give your campground a professional public face. With this you can network with your group of contacts on social media sites. Getting your campsite known to the camping public may take some initial promotion on forums targeted at campers and RV's. Using social media sites will spread the word fast, so start promoting.