Will it attract predators?
I don't have that problem. I leave mine locked in the coop and run when I butcher so they cannot see what I am doing. It also keeps them out of my way while I butcher. When I let them out, some always find where I was butchering and they clean up any bits that hit the ground that I missed. I do have predators that come around, whether I have recently butchered or not. I handle that by keeping them locked in the coop at night.
what do you do with all the blood and guts?
I let the blood soak into the ground. I keep a water hose handy and am constantly rinsing off my work area, hands and the chicken parts. I really don't notice an accumulation of the blood. For the feathers and other parts I don't use, I dig a hole and bury it. I have not had a problem with anything digging it up, but you can put something over where you buried it if that is a problem. If you live in the country and have the room, you can carry it off into the woods or such and let the scavengers clean it up. My trash service specifically forbids butchered animal parts. Some people compost the remains. Depends on your set-up.
If I can get someone to kill and gut them off the property how long do I have before they need to be plucked?
I pluck mine before I gut them. It seems a more natural way for me to do it. I'm not sure I would want to scald a bird that has been gutted. It would probably be OK but I'm not sure how the meat inside would be affected by that hot water. I also do not throw everything away that I get out of the bird's insides. I eat the liver and use the gizzard and heart in the broth. If I butcher a pullet or hen, the dogs get any undeveloped eggs. The dogs like butchering day.
We all have different situations and set-ups. I have plenty of room and my neighbors would not be upset that I am butchering if they were close enough to see what I am up to. If I lived on a small lot in a suburban area, it would be totally different. I'd think if you get someone to kill and clean them, you could also get them to pluck them as part of that process. That would probably work better for you.