@Christine2582 There isn't any reason why a host has to offer accomodation to a health worker for free, unless they want to. It's a generous offer, and wonderful if you can afford it, but not required. There's no reason why it can't be offered at a discount, or at least for enough to cover the expenses of someone staying, like utilities, cleaning, and whatever amenities, like tea and coffee, snacks, paper products, or whatever a host normally provides. No need to make a profit, but also not necessary to pay out of pocket for those things, if it's a financial hardship.
Sometimes the worker's place of employment may cover the cost of temporary housing.
If you do offer to house medical and other essential workers, it would be a good idea to remove any extraneous things from the rental unit. These workers need a place to sleep, shower, and cook. They aren't relaxing on holiday, so you can pare down what's there- purely decorative items, throw pillows, lots of extra dishes, etc, won't be needed, and if you remove them beforehand, there will be that much less to clean and sterilize properly.