Earlier quoted context omitted.
As someone who isn't used to taking upfront payments, my question is, are people actually willing to do that?
Yes, definitely. I just did that for two projects in the past week; but it was 1/2 up-front. Albeit, they were close referrals. YMMV if it's potential customers who don't know you.
I've never had anyone walk away from a project after asking for 50% upfront at projects this scale.