We have been on trustedhousesitters (as sitters) for two plus years.
Our experiences have ranged from positive to extremely positive to practically perfect.
Most normal job-interviewy type stuff applies here, too. We make sure that our references, background info, and cover letter are all be error-free and positive. We also took all the steps to be super-certified in their system.
Since you are asking for fairly specialized care for one pet, I would look for someone with that specific experience (giving meds, administering shots, expressing glands, etc.).
Asking a sitter to pay for utilities would be an immediate deal-breaker for us, especially with a high-needs pet included.
The best part of sitting for us is allowing pet owners to travel worry-free, and allowing their pets to be happy in in a normal-ish routine.
Best of luck in your search.