Unless you have major repairs to do on a property during the turnover period it's likely that you'll be showing the property to interested applicants while your current tenant still lives there. This is a common practice and if the outgoing tenant has had a pleasant experience in their home, is leaving of their own free will, and is a thoughtful person, you'll likely not have any trouble in this. Many tenants will make sure that the property is picked up and cleaned up to the best of their ability during this time (though you may have to forgive the clutter that always comes with packing and moving) as long as you give them enough notice that you'll be dropping by.
Before the tenancy even begins it is a good practice to put into the lease just how much notice that you will give the tenant. Some local and state laws may dictate that you're required to give warning a set number of hours beforehand. Make sure the tenant is aware of this when they move in so that when it comes time to move out that there will be no surprises on that front.
If a tenant is being evicted or if you are selling the property and showing it to potential buyers you may find yourself with a less cooperative tenant. They may not be as willing to pick up the property and make sure it looks its best. Often applicants interested in renting the property from you or potential buyers will understand this, but in the end it will make it easier for the tenant if they do keep it picked up. That means they'll have that much less to clean when they leave and will receive more of their deposit back.