Does he still have to have a signed leased? If the tenant refuses to leave, what are the consequences? How long will it take to evict a tenant

All leases become month to month after they expire if a new lease isn't signed.

Why you would want to rent month to month from day one is what I don't understand... if they leave after the first month you will be in the hole prepareing for new tenents most places.

Eviction is actually easier without a lease. You just have to provide the locally required amount of time advances notice that you are terminating the month to month lease effective **** Usually the next full month as 30 days advance notice are what's normal most places. If they don't vacate file for eviction at that point without delay. Some places will allow you to jump start the actuall eviction paperwork by allowing it to be filed before the 30 notice is actually past.

Contact a local relestate lawyer to be sure the proper notice and that they are properly served comply with the law to avoid delays.

You are not typically required to let them stay beyond the period of a contracted lease most places... (30 days without a contract).

But laws vary, so you need to be fully aware of your specific regulations for your City, State.