Thank you all so much for replying.
In answer to the 'who pays for....' questions, I have it in writing (well WhatsApp, but that's still writing). I'll call the landowner Bob to keep things short!:
Bob will pay for all costs. That's the outlay for sheep, transport, hedging/fencing materials, vet bills/medication, feed stuffs, supplies, adminstrative costs, equipment... everything.
Bob has said that the only time we'd be expected to pay vet fees is if we insist on limping a sheep along on expensive daily medications when clearly the right thing to do is dispatch.
We are the 'sheep keepers'. We decide what they eat, Bob buys it. We decide what sheep are bought to an agreed budget. We decide where the sheep are bought from.
When the sheep are in lamb, we decide what happens with the offspring.
The only 'payback' is that Bob has half the meat of any slaughter and if we want out at any time, we will discuss whether we sell our half of the sheep to Bob, sell all the sheep and split the money, or slaughter all the sheep and split the meat.
The way Bob sees it, they are happy to invest and we earn our half by looking after the sheep.
We have chosen, rightly or wrongly, some Zwartbles. We can't at this time go big in terms of flock, although we've already been told that someone with a field that Bob knows would be interested in us keeping sheep there, too.
I have double and triple checked that there will be no financial outlay on our part. I don't mind losing time and I wouldn't even mind losing money that is generated from the farming process, but I don't have money to plough into someone else's land.
Bob is adamant that no money changes hands. They run a barter style farm and have done for years. They have all sorts of arrangements with local people. E.g. Someone keeps bees on a section and in return they give Bob some honey.
We've already been to see some sheep and Bob gave us the money to put a deposit down on them. Bob has already paid for the hedging we've put in and bought the fencing supplies to double fence the boundary.
I genuinely think it is a genuine offer. Also, we've agreed that the review period will be quarterly, with no obligation to continue.