I have never had a vet come look at my birds, my father never did, my grandfather didn't, nor did my great-grandfather. Actually, other than a few people on this forum most people never even suggest the need of a vet for your birds. Worming though, if you want your chickens to live is a must unless you keep them in a place it would be impossible for them to catch worms from which is not an easy task. Even if you kept them in your basement off the ground, a roach could still crawl up into the pen, become ingested, and in turn infect your birds with worms.
How you worm your birds is up to you, I personally use Safeguard and Ivomec; I plan to worm twice a year, but if I ever feel one may need it before the appointed date I'll worm him then. Any new birds I get are wormed upon arriving on the yard usually, unless I don't think they need it (i.e. the person wormed them) and then quarantined for a allotted time. Other people worm monthly, some worm every couple months, some only worm when they feel it is needed; your method is your choice but out of all I'd suggest the least likely rather than the most likely myself.
If you don't take the vet route, you can also study into chicken diseases yourself and learn to identify and how to treat them. There are a lot of books out there, I personally like Chicken Diseases by Fred P. Jeffrey myself, only costs about 6 dollars; but there are a lot of other books available online for free, libraries possibly, and so on if you look around. I even know of a place where I personally have linked free online books you could look over.
God bless,
Daniel.
