Similarly, you may ask, what do you say when someone asks how much something costs?
Just say, "You know, talking about the cost of things really makes me feel uncomfortable so since I consider you a friend, I am going to avoid that discomfort. I just don't want to talk about money." Then have a different subject ready and immediately plow into a new subject to avoid a different kind of discomfort.
Likewise, how do you ask how much to charge for a friend? Call said friend and say, “I like your work and I'd like to sit down and meet with you about your photography packages and prices.” Then when you go MAKE SURE they have a contract, even though you're friends and they might want to give you special pricing, they need to have a contract drawn up for you.
Additionally, is it rude to ask someone how much their rent is?
Depending on the exact situation, it can been taken as extremely rude. It comes very close to simply asking them how much money they earn. While some people live far above or below their means, most people have a strong connection between income and rent (or mortgage) payment amount.
How do you ask someone to pay for something?
Ask for the payment simply and be straightforward. Tell them you have included the invoice as part of the email and how you want to be paid. The conclusion is polite and lets them know that you'd love to work more with them in the future.