You can have as many keys as you desire. It's good practice to use separate private/public key sets for different realms anyway, like one set for your personal use, one for your work, etc.
First, generate two separate keypairs, one for home and one for work:
ssh-keygen -t rsa -f ~/.ssh/id_rsa.home
ssh-keygen -t rsa -f ~/.ssh/id_rsa.work
Next, add an entry to your
~/.ssh/config file to pick the key to use based on the server you connect to:
User <your home acct>
User <your work acct>
Next, append the contents of your
~/.ssh/authorized_keys on the work machine, and do the same for the home key on your home machine.
Then when you connect to the home sever you use one of the keys, and the work server you use another.
Note you probably want to add both keys to your
ssh-agent so you don't have to type your passphrase all the time.