I know that your first instinct will be to scream and shout and strangle the person nearest you. Try to stay calm and professional. This will be a challenge, but I think that it’s important. Again, they are leaving, and you want things to go well, both for the sake of your business and your property.
Your goal is to continue to collect rent until it’s rented again, and to have the property left in good condition and maintained while empty. Yes, you will have extra costs from fixing/improving this and that between renters, and perhaps realtor fees, but if you can minimize the other expenses, then you’ve done the best that you can do under the circumstances.
Remind your tenants that they’ve signed a legally binding contract, and that they are responsible for the remaining rent (and perhaps utilities, lawn and pool care, etc). But here’s what you can do for them (yes, put it that way, you’re willing to help them with their unfortunate situation!): as soon as the new renters are moved in and paying rent, they can stop paying rent to you (and utilities, lawn and pool care, etc).
I’ve been faced with this three times in the last year, and you’d be surprised how well this works! All of a sudden there’s a financial incentive for the current tenants to start showing the property and keep it looking its best!
Normally I have trouble getting tenants to show the property when their lease is over and they’re leaving, and usually I have an empty property for about a month until new renters move in. In this situation, instead of having an empty property that I’m paying for while finding new renters, the prior tenants cover my costs.
It basically comes down to this: you’re in a situation where you have lost your renters early and that’s not going to change. You will incur extra costs, and that won’t change. Why not make it work to your advantage the best you can?