Money pit? Possibly but on a forty year lease we’ll not be around to worry too much. The van itself is said to last about 25 years in rental condition.
You’ll be extremely lucky to find a site owner who will let you keep a 25yo van there, though, much less for 40 years. There’s loads more profit in it for them if they can have a hand in every stage of frequent turnover with new vans – even if you keep it looking like new, they still won’t want to know. It's the equivalent of expecting a credit card provider to be thrilled that you've used it so responsibly and made sure to pay it off in full every month!
Tourers are a good alternative but not everyone wants to tow, plus you need a big expensive car as well.
You can tow a decent-sized tourer with a normal family estate car. Some of the massive double-axles will need a powerful, thirsty 4x4, but plenty won’t.
What Bwlch has sounds amazing. The caravans themselves are fantastic – it’s the greedy site owners who make them into money pits. If you’re able to find a nice farmer or small landowner who’s happy to just get a decent rent for the use of the land, without wanting their fingers in every other money pie going as well, that could be a perfect solution. Obviously, you wouldn’t have all of the amenities you’d have on a site, but if you just want a home from home with basic facilities, it could fit the bill perfectly.
I’d second the tourer suggestion - on a seasonal pitch, if that’s what suits your needs. Site owners for tourers seem content to make a good living by charging fair prices for the use of their land and facilities, without wanting to be Del Boys, taking you for every pound they possibly can whilst handing every scrap of responsibility straight on to you.
I think the most important thing to remember is that it is NOT an investment in any way. Add up the cost of buying the van and ALL of the site fees over 10 years (including mandatory fencing/decking etc that has to be installed by the site owner’s nominated fitter (whose charges will include a mighty kick-back for the site owner), plus utilities, insurance and other bills (including repairs) and then divide them by 10 – and that’s what it will cost you per year to have it. Once the 10 years are up, expect to walk away with nothing left, no assets or money left in it, and to be right back at square one.
Also bear in mind that, if you have school-aged children, you will be limited as to when you can go for full weeks, depending on the school holidays. Plus, if you hope to get some money back by renting out, any families you rent to will only be able to go there for the same few prime weeks that you can.