EDIT: The below were my feelings at the time. My position now is that I won't pre-pay before hearing or seeing someone real-time in some way, am open to partial pre-pay after that, and will only fully pre-pay in-person (all if I'm still comfortable with you of course). My post was not meant to interfere with legit pros, just scammers and shady ones. Yes, guys can be shady and scammers too. PS it's OK to express your opinion on topics but not attack people, especially not repetitively or across threads. Thank you.
ORIGINAL POST:
Don't do it. It's how scammers operate. I've been scammed before this way. Unless someone's got an established business location that you can go visit, don't ever pay before knowing they're real. It applies in anything, real life, online, and here. I've been paid for services and I never needed the money first. Neither does anyone here.
If someone here requires payment before you can see or hear them interacting with you, state you'll do it when you know they're real. Even then I wouldn't recommend it until you're halfway through. If they decline or are rude or block you, be glad you kept your money. It's an unreasonable expectation. Most have been nice and trustworthy here. Trust but verify. That's all I have to say about it.