If SE ever billed me a single penny for asking a question here when I was a 1-rep user, I would never bother to ask it since I could ask somewhere else or work harder to solve my problem on my own. Also, I'm pretty sure that many people share my opinion.
It is even worse than that. Asking for a payment to allow a question is something that seems to be extremely scammy. I immediately close the page or hit the back button when I see any site unexpectly asking for my money.
If the model is billing for answering questions, I don't even need to elaborate further of how bad that idea is.
Further, not everywhere in the world people have access for international credit cards. I for example (live in Brazil), don't have one and don't know much other people which do. So, I probably couldn't pay even if I wanted to.
Another suggestion is to offer a freemium ad-free version of the site. However, why would I pay to remove ads if I can just use an adblocker for free? BTW, nowadays that the internet is full of tracking spammy audio and video porn ads mining bitcoins everywhere continuously abusing my browser, my CPU, my memory and my network, I never ever turn off my adblocker and configure my firewalls to try to block ads to the greatest length possible so they don't overload my network with junk traffic. Also I actively tries to persuade other people do the same. That is getting so bad that I'm starting to hate people who don't have an adblock and hating much more people who actually click on ads, specially those that are clearly spammy/scammy or resource intensive. SE sites used to be trustful, but they aren't anymore. Also, a business model that works by creating problems (a bunch of ads) just to sell solutions (adfree) is not sane and probably not long-lived.
If SE needs better ways to earn money, billing people for asking questions, posting answers or having less ads is not the way to go.
Some suggestions are:
You have a job site that works great for SO AFAIK. Invest in that for other areas too.
Promote or sponsor events/meetings/hackatons/whatever and get a percentage of the registration fee. I'm pretty sure that if SO promoted or sponsored some event about, say Java, in some city and for a price that are accessible for me, I would surely do the best to attend it. Of course, you have plenty of options here, from SFF to math, to a lot of areas of programming areas and even to bicycling and cooking.
Allow people who want to post non-Q&A content (for example a blog) in SE network do that for a fee and get it promoted in the network somehow.
Sell t-shirts, cups and other things like that. I would surely buy some if there was some way to do that (even if I needed to borrow the credit card of some friend, with his/her consent).