On the CAR form, section 29, there is a section where your rental agency could have made a 30 day notice a condition of moving out. If it is not marked, this is what I would do:
First, email the tenants and outline the lease terms reminding them that unless otherwise informed, you are assuming that they are moving out at the time of expiration. Of course, if they had been good residents, you will want to make it a nice: "You guys have been great tenants and I hope that you will renew for another year!" In the email, make sure you give them a deadline to let you know by. Also, it might help to attach a renewal so if they plan to, they can sign it and mail it back to you.
Second, if you dont hear back from them before that requested deadline, I would put a 24 hour notice for entry on their door so that you can look at the condition of the home, but I would tell them that I have to enter to show a prospect. Then bring a friend with you acting as the prospect just in case they are home at that time.
Doing this nicely should light a fire under their butt in keeping you informed of their decisions. Just be upfront with them in your initial email about how you dont want to kick them out on the street but would also like to be able to budget properly for marketing the rental property if they choose to move out. If their reply email is still unclear, give them a call or go visit them.
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Evictions cost a lot of money and take a long time. You will lose about 2 months of rental income and there is a good chance they will be pissed off and may do damage to your home. Evictions only make sense if they refuse to leave and refuse to pay rent.