We have 6 hybrids (brown laying hens) and 2 bantams at our allotment. Our run is secure against foxes so they let themselves in and out.
Feedwise, 2 bags of pellets costing about a tenner from local feed shop, lasts about 8 weeks. A sack of grit lasts 6 months. They also have allotment scraps and the odd naughty left overs of bread, veg etc (it's naughty because defra rules say you shouldnt feed them anything that has been in your kitchen).
Our run is part slabbed (as soon as we find some more freebies it will all be done). In the winter the bits that aren't are a muddy mess. So would definitely say some kind of hard standing, and ideally a roof on a run at home. It's not so bad at the allotment though.
I do let them free range when I don't have things growing they can hurt. So from October onwards until around May, but only when I am there.
Rats are an ongoing issue. I use hung vermin proof feeders which does seem to work as I know from the amount that's getting eaten if we have rats making the most of the buffet. But we are on an allotment with other allotmenters keeping chooks so not much I can do about that except try and keep them out of my feed.
Personally I love them. They all have different personalities, are the nosiest pets we have, always wanting to follow us around and interfere. They know the sound of my car, know me and my husband and can see if I have a bag of treats before I even get in the gate.
They are funny to watch, easy and cheap to keep and the eggs are lovely. I go once a day to check and feed them. I clean them out once a week. Takes about half an hour, maybe 40 mins in winter when I am cleaning the slabs and putting fresh straw down on the slabs.