A couple of the Kennedy halves and an Ike dollar were only available from mint sets, so I did purchase these and break them apart to obtain them for my set, as it was significantly cheaper than buying the single coins. As far as the Lincolns go, I believe all business strikes were issued for circulation, so grade would be your primary consideration. Mint sets are cheap, and you could recoup some of your costs by selling the other coins. I get my modern circulation strikes (quarters and halves, along with the past two years of Lincoln cents) from a flea market vendor. I'm sure there are web sites that do sell modern coins, a Google search should start you out.
















