There's no doubt a lot of firms doing welfare unit hire now but demand is outstripping supply so there must be room for a few more. Don't know how much they are new (I'd guess around £20k) but a decent 2nd hand unit is around £12k now in refurbished condition which is what you would want to start a hire firm with IMO. The formula for hire is pretty simple;
Unit £12k
Hire rate per week £150 lets say. I cant get one for less than £200 round here, but obviously long term hire is always a bit less. £150 sounds reasonable.
80 weeks hire pays for it, but its not quite that simple...
Delivery is always charged extra, £50 on average in my experience. Same for collection. That should help to cover fuel costs but not really your time as well or wear and tear. So lets say for every unit hire - delivery, collection and prepping it for hire takes you 3 hours. That's an hour for cleaning/ prep (check oils etc) and an hour to deliver and return, with another hour to collect and return. £25/hr for your time, plus fuel, truck wear and tear wont be covered by the delivery charge and will come out of the first weeks hire. Which is ok - you can set minimum hire terms of 4 weeks for example. Many do that round here.
Insurance, servicing, tyres, brakes lights etc will need to be covered, as will somewhere to store it which costs regardless of if the cabin is in the yard or not. £250/ month for storage rent? Lets say £90/ week should cover all costs?
So on a 4 week hire, you will have a gross of £700 including transport.
Costs will be £435 leaving you with £265 profit before tax. Doesn't sound so good with only £60/ week paying the cabin back (200 weeks hire to pay off now) but lets not forget its a 37% margin and many aren't making that.
Now that's worked out based on one cabin and some assumptions, some of those costs will be diluted by having more cabins so the margin will increase per cabin as you get more.
There is also the thing in plant hire of any kind where the asset is worth something after its useful working life. Lets say it does 3 years and halfs in value. Plenty on the market for £5-6k so that seems reasonable. It only has to pay back half of the £12k now, (100 weeks hire) 2 years worth of weeks that. And the 3rd year is therefore more profit.
Doesn't seem like a bad business model to me, and its one I have considered myself if I'm honest. But you would need a few of them to pay you a wage and the utilisation wont be anywhere near 100%, especially in the first couple of years where the uptake will be slow. But its a pretty low risk venture really. You can always sell the unit if it doesn't work and not loose a huge amount of money. At least you can say you tried.