Well here's my experience on the subject. I got chickens purely for eggs but I wanted a rainbow when it came to the color of eggs in my basket so I didn't stick to just one or two breeds. I have 7 different breeds of 10 hens. Pretty much all my chickens with the exception of 3 are dual purpose breeds so technically I could butcher them for meat too. I got a few of mine straight run and then 4 I got from a hatchery and paid extra to ensure they would grow up to be hens.
Looking back, the chick process was fun but not economical. If I were to do it over again, I would not buy straight run (unless it was a breed I was dying to have) because I ended up with more roosters than I wanted and trying to find them homes was very difficult. I don't have the heart to kill the poor things. The energy, time, and feed put into the rooster starting from chick to big enough to eat would not be worth it to me. I would recommend spending a little extra money and buying pullets or chickens that were just about to start laying anywhere from 4-7 months old. The first year to two years is when a hen produces the most eggs after that it is a gradual reduction. If I were you I would butcher the older hens when production dropped. However, if you did that you might be waiting awhile for meat. You could go straight run and butcher the roosters but once all your roosters are gone then what? Not to mention the time spent waiting to figure out if they are roosters.
Have you thought about getting a mixed flock of egg layers and meat birds? If you got cornish cross chickens you could breed them which would give you a constant supply of meat birds. Birds bred specifically for meat develop and mature at a much faster rate. I believe Cornish crosses are ready to be butchered in just 8 weeks. This is much more economical to feed a bird for 2 months and butcher than after a year or two. Then you could get birds for eggs and increase your rate of egg production. When an egg layer got older or egg production decreased you could butcher her too. Then buy a few more pullets. This option, to me, is the most economical. You're spending less money, time, energy on birds that develop much faster than going the dual purpose route. Just an opinion. Whatever you decide to do good luck!