It has to be said from the outset that diy hovercraft plans don't have a great reputation on the internet, but before going any further we should differentiate between what we mean by diy hovercraft and hovercraft kits. A kit normally includes everything you need, or mostly, together with a set of plans to showing you step by step how to construct the craft. You shouldn't have to provide extra materials, as everything is provided - it's important to check the contents on arrival to make sure nothing is missing, by the way. The do it yourself option may just include the plans, with you having to provide all the equipment yourself. Both options have pros and cons - where to find hovercraft.
All ready made hovercraft for sale have gone through rigorous quality control, so you can be sure that it's as safe as it can be, but this may not be the case with the other two options. For example, even you are proved with all the correct materials, the construction process is in your hands, and the documentation will surely have a short clause somewhere in the fine print pointing out that the ACV safety is your responsibility. the good thing here is that the materials provided will be suited for their function, so you don't have measure, cut or guess if a certain material is strong enough, or flexible enough for the job.
With a do it yourself kit, not only do you have to build according to someone else's plans, but you have to get you own materials, even down to the engine. It's true that this choice really does reduce the hovercraft cost, but if you are on budget there is always the temptation to skip a little and use material that is not quite up to the job. For this reason, DIY kit plans will also have a clause stating very clearly that the success of the project, and the safety of the finished product is in your hands only - in short, it depends upon building the thing exactly as instructed and using materials that fit the specifications precisely.
After all it may be so much easier to by a personal hovercraft, but the big thing is the cost. A ready made craft will cost anywhere between $5000 and $14000, while a DIY kit costs in the region of $2000. By far the cheapest (and most difficult) options is to build it from the ground up using professional plans. If you are short of money, have a workshop and are useful with cars and machines, then this choice may well fit the bill.