Just do not make it the first ad only question you ask. I was so turned off by nannies I contacted to do the initial phone contact whose only comment / question was what is the pay. I think the best way is to ask a few other questions and then say you look forward to meeting but want to make sure we might be compatible on the price so could MB ease give you a range they are targeting for pay ?

It's fine, but the proper form is to ask what compensation range they have in mind, not what they "can" pay. What they can pay and what the intend to pay are two different things.

Sure, you can ask what range they have in mind.

Is it rude to ask how much the parents can pay over the phone before even meeting them in person?