abailey :
Some can do like you want but you will suffer a big hit to performance. More than a 50% reduction in max throughput on your wireless (including the devices attached to the Ap) The better option would be to purchase a client bridge device to attach wirelessly to your main wifi router and then put a wire between your client bridge and your second wireless router, running in AP mode. Then set your 2.4Ghz channels to 1, 6, or 11. Making sure to use different channels for your main router Wifi and your AP wifi. Now if both your routers are dual band you might be able to set it up right with just the 2 wifi routers.
Do you think i will be adding a repeater or something? The second router will be connected to the first via ethernet, not wirelessly like a bridge. I would then disable DHCP on the second and make the SSID and password the same as the first, that is my plan, isnt that what an AP is? Both are dual band, btw. Also, if i dont want to drop wifi when moving between stronger signals, both routers have to have their frequencies be on the same channels, right?