I have a couple and their daughter rent two bedrooms in my house since Dec 2006 at the rent $500.00 for each room. When can I raise the rent and what is the maximum percent can I increase ?
Thanks.

You can raise it once their contract/lease is up. I don't know about the maximum percentage increase..

That depends on local laws. If you are just renting out rooms, you probably aren't covered by most rental laws.

Did they sign a lease or is this a month to month?

I have a couple and their daughter rent two bedrooms in my house since Dec 2006 at the rent $500.00 for each room. When can I raise the rent and what is the maximum percent can I increase ?
Thanks.
No lease signed.

You can do whayever you want with 30 days notice.