My sister had some broiler birds a couple years ago that she was too lazy to butcher. She ended up keeping them for several months before finally selling them to someone as live birds. They got very very large and had legs like tree trunks! lol
They were kept on free range and were not given any commercial feed. She has a very large property for them to roam and no predator issues... anyway...
You could try holding them if you want, and they may do ok on a free range diet, but they will still not live as long as standard breed birds, and if you hold them too long they will have no usefulness for meat either...