Hello and welcome.
I would say - sales speak applies.
(a)
As far as the length of time that you can keep the van on the pitch, this entirely depends on what your contract says.
No matter how nice the sales person, do NOT EVER rely on anything you are told about how long you can keep it on site unless it is in writing.
Yes, a 2012 static can easily last 10 or more years.
This does not mean that it can remain on the same site - you need to know what age limits the site allows.
Some contracts specify a set period (usually that after a certain age, which can be as little as 10 years, the van has to be replaced or removed).
Some contracts do not specify any period, they are rolling contracts that are intended to be renewed annually - which means that your terms and conditions, including whether you can keep the van on site, can be changed or terminated at the whim of the site owner.
(b).
If you need to rent the van out to cover costs, then it is possible that owning a static is not a good idea.
It is unlikely that you will recover all costs, you may get enough to cover the annual pitch fee - but there are a lot of costs and legal duties associated with renting out a van, it needs a lot more research than just asking on a forum.
The sales person has probably indicated that renting out your van is a guaranteed way of recovering costs - if it was so good, why are they so keen to sell you the van instead of keeping it and renting it out themselves?
The park cannot lose - you still have to pay all the fees and running costs whether or not anyone is renting it (and a 2012 model will be at the lower end of the revenue stream).
Ask the park for a breakdown of costs involved - including their fees for managing rental ad whether they guarantee any income.(and again, in writing).
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