The nutshell version of what I wrote below is I agree with aart to start with fewer meat birds, perhaps 10, if you plan to process them yourself. If you plan to have someone else do it, find out if they'll come to your place to do it (do you want them to?) or if you'll need to transport them. If you need to transport them, find out if they have cages available to borrow or if not, what sort of transport cage/box they require. And you'll need a vehicle big enough to transport said cages.
I ended up processing I think 23 various chickens for meat this last fall. I had never done anything like it before, the only thing I've ever gutted before was fish. I skinned most and plucked a few. The barred rocks were much easier to pluck than the dark cornish. I skinned all the roosters because they were too hard to pluck, way too many pinfeathers. The roos were all about 5 months old and I think given another month or so most of those pinfeathers would have developed into easier to pluck real feathers. Depending on my other chores, I could process 2-6 birds a day. I got faster over time, but it still took me a long time. Part of it all was the set-up each time...table, plastic on the table, drag the hose from the backyard, sharpen knives, find the pellet gun for killing the chickens, etc. I also didn't want to be killing chickens in front of the others, so I had to go around the building to do it...all this sure added up the time! I also spent nearly every weekend in the fall, right in the prime of hiking season around here, processing chickens (amongst other chores, but the chickens took most of the time). It was a fun learning experience, but I don't want to spend all next fall doing it again. There's a farm nearby that will process them for $5/bird, which is rather high compared to folks in other parts of the country, but it's the only option I've found so far. But we didn't get into raising our own chickens necessarily to save money, but to raise our own high quality meat.