Just like with elderly humans, the needs and temperament of Senior Pets differ from adult pets.
You need to be wise when having a meet & greet with a Pet Owner if they have a senior pet. Demonstrate to the Owner that you have taken the time to research the needs of senior pets and show how you can make small changes to adapt your home to suit the needs of older pets.
If their senior pet has a low noise / low socialisation tolerance level - You need to ask the Owner if a solo booking will be required (ie. not accept any other booking requests for the time senior dog or cat is staying) and perhaps ask them to pay a little higher for you to forgo other bookings with pets who can tolerate other pets and who are socialised and perhaps require less cleaning.