If you do not want to be responsible for the domain name or hosting, refer the clients to the hosting provider so they can pay for the hosting themselves. Might not be as professional. Depends on your current relationship with the client.
That will look pretty unprofessional. There are going to be ongoing costs like this in any business. If you really don't want to handle hosting (I don't), I suggest you develop a relationship with an existing host and arrange to have all your clients referred to them.
let them know that you do the design and development but they need to get their own hosting provider. if you want to do a good job in your recommendations of hosting make sure you have done your homework and you can present a proposal of why you have recommended that hosting provider or providers from them to choose from. There are referral programs you can join when you refer clients to them for hosting and domain names.