Oh dear, as requested, one reality check coming up..........
See what the estate agents have to offer in the locality you want to go to. Look at the prices, see where you can afford to go to, and see what is / isn't allowed on anything you might be interested in.
From what you list you want to do, you may well need planning (sheds, animal shelters), or even change of use.
To look after animals properly you need to be able to keep an eye on them - more than once a day every few days. In that situation I don't recommend you have animals. Animals need shelter, water, winter feed. What happens if you can't get there, for example through all that snow we've just had?
What happens in an emergency when you have to drop everything and get there fast? What if you don't have what's needed to deal with the problem - you can't just nip home and fetch it. At the very least you have another unexpected trip to pay for (and need the time to do it).
Remember, you need to register to be able to keep some animals, e.g. sheep, pigs. And keep records.
Veg needs water too, so you really need to need to take into account where that is coming from.
You say you want it near a train line, are you going to bring everything you need with you to tend the site on the train? Hope you don't need a rotovator then. Even a spade is a pain in the bum to carry about. And you can be sure you will forget to take the one thing you really need.
And if it's all kept on site - well, if you aren't there to keep an eye on it all, some of it might go 'walkabout' including stock or anything you have in your shed if/when you have one. Doubtful an insurance company will cover that (but worth asking).
Then you will have to pay for it all ongoing as it doesn't end with the purchase of the land. Besides stock, seed, plants, tools, fencing, upkeep, there are travel costs, taxes, insurance, water bills, registration fees.........
Ah well, that's some of the down side.
Get your head around that lot and you are on your way!