I raise meat birds and keep a few egg layers for my family's consumption. Here's my opinions on your questions:
1. Length of time to raise meat birds is dependent on the type of bird you raise. The standard is the Cornish X-rock which reaches butchering age in 8 weeks. I raise Freedom Rangers which reach butchering age in about 8 - 12 weeks, with roosters maturing quickest.
2. When I order meat birds, I order a "straight run", which means I get a mixture of males and females.
3. Meat birds are entirely different in behavior from "regular chickens". Meat birds eat a LOT of food and depending on the type of meat bird, will either not free range at all or do so very similarly to "regular" chickens. X-rocks do hardly any free ranging, while Freedom Rangers are close in nature to my egg layers.
4. Some people, such as myself, raise meat birds and egg layers. Others raise "dual purpose" breeds. You just need to decide what works best for you. The way I got started was from McMurrary.com's "bacon and egg" special. It's a combination of 10 egg layers and 15 Cornish x-rocks.
