It will depend on how many times a year you intend to go away, but if your looking at seasonal sites, then it might be worth looking at alternative strategies such as renting a caravan, or using ABB's etc
If you add up all the costs of establishing a touring caravan, such as changing or modifying tow car, Cost of caravan, site charges, not forgetting winter storage, servicing, keeping gas supplies topped up, the worry about it being damaged or stolen, repairs insurance etc you might fid the alternative are more palatable.