It totally depends on its processing power. The more Hashes it can perform per second, the more income it will generate you. Keep in mind that the more hashing power comes online, the smaller your piece of the cake gets. There are 3600 Bitcoins distributed every day (on average, it fluctuates due to variance), they're effectively distributed between everyone, who is mining, depending on their respective hashing power. The more hashing power gets online, the less your piece gets in comparison. - This is a very simplistic explanation but it should give you a rough idea!
It also depends on how much power the miner consumes... The more it consumes, the higher your electricity bill will get!