April 08 was the first time I got hens: two ex-batts. I read up loads of information beforehand... worms.. mites.. lice... foxes.. badgers.. mink... sour crop.. egg-bound.. aiiee! Talk about panic. So I understand your concern. The concern is good as it makes you think about predator-proofing your hen accommodation. It makes you get everything ready before you get your birds. That makes it much easier on you & the birds in the long run.
I made sure I had everything in place first. Accommodation, bedding, substrate for the enclosed run, food & water containers, wormer, food, etc.
When I collected the birds they went straight into the new accommodation. I started worming them & started mite control on the day I got them - the condition some ex-batts come out of a battery farm is appalling and it's not unusual, apparently, for ex-batts to be riddled with parasites to varying degrees. So I erred on the side of caution. One thing I did worry a lot about was the girls sorting out their pecking order. In the first week there were some fights that *looked* dreadful. BUT - there was no serious blood drawn, so I let them get on with it and I'm glad I did as it was over quite quickly and harmony reigned.
Have to say I don't regret for one second getting the girls. They are such characters and the eggs I view as a rather delicious bonus. I've also found that they are no hassle to look after provided I make sure that I spent a few minutes (literally a few minutes) each day cleaning out the henhouse of overnight droppings, giving clean food and water and giving each bird a swift visual once over to check for external parasites - I hope that in that way, should any problems develop, I catch them at an early stage so the matter can be dealt with more easily than with an ignored & than ingrained infestation. I also worm them every month with VermEx and the girls seem remarkably healthy.
The girls have been so easy to look after (I deliberately only got a couple to start with as I didn't want to get a lot and them find myself overwhelmed and not coping, as that wouldn't have been fair on the birds) that I'm going to get some more. Once I've extended their run area that is!
In this first year, I haven't learnt everything there is to know about hens, but I have learnt what fun they are and how easy they can be. I recommend hens!