As others have mentioned, there is a big difference between fast-growing meat hybrids (commonly referred to as Cornish Cross), slow-growing meat hybrids (like Red Rangers), and dual-purpose chickens. They suit different needs.
If you want the lowest cost meat available... honestly, go to the store.
If you want to raise your own, but cost is important to you, fast-growing hybrids are the most efficient. In my experience, they are less expensive than "fancy" breeds. They consume less than two pounds of feed for every pound gained, and they reach butcher size in 6 to 10 weeks. One of the bigger challenges with them is that they produce a lot of feces in a short timeframe. This can be managed, but I've seen a lot of situations where it gets out of hand because birds aren't moved often enough outside or there are ventilation issues in indoor housing. Housing for these guys can be pretty basic - they need protection from getting too wet, too cold, or too hot. Your climate will determine when they can go outside, but people commonly raise them indoors for 2-3 weeks and then let them spend the remainder of their lives in mobile pasture pens. Most people don't provide them with a roost, but I always have a few that don't get the "broilers don't roost" memo.
If you are (or want to) raise birds that you can breed yourself, dual purpose males can be a decent choice (or at least, an existing resource to make use of). They take longer to reach butcher size (16+ weeks), so you have them a lot longer. The advantage is that they can be processed over a period of time, so you can store your meat on the hoof so to speak. They are less efficient using their feed (rule of thumb is 4 lbs of feed per lb of gain), so they do cost more to feed to the same final weight. They are also less meaty. For the same live weight, you will get substantially less breast meat and less meat overall. I like to provide these guys with roost space, and they will generally use it. Of course, some of my birds (including layers) seem to prefer sleeping in piles on the floor, so you don't have to have roosts if you don't want to. I generally brood these guys for at least 6 weeks before moving them outside, though you could do it sooner with the right weather conditions. I currently have 8+ week old birds inside because our weather/timing hasn't lined up properly yet. They aren't as bad as having the fast-growing hybrids inside, but I'm ready for them to be outside.
Slow-growing hybrids can be managed similarly to dual-purpose males. Depending on the hybrid and your specific situation, you can expect them to reach butcher size in 9 to 14 weeks. These birds are usually less efficient than the fast-growing hybrids (requiring a little more feed for each pound gained), but they are more efficient than the dual purpose males. They usually dress out similarly to heritage breeds, so you'll get a little less meat than an equivalently sized fast-growing hybrid. Roost space can go either way for these guys. They will generally use roosts, but they'll get on fine without them as well.