Welp...I've run a commercial broadcast studio for nigh on to 25 years now and we've been skint, burned and downright screwed many a time in all those years. We...mostly due to being business to business...are on a net 30 basis. Which usually means net 90...180...whenever sometimes. We do charge rather hefty late fees. Which some a-holes (I mean, valued clients) just ignore...bastids. And in all those years I've never sic'ed a collection agency on anyone. Dumbass me. We take every new client that walks in the door and just hope for the best. One reason we can do this is most of the time our bookings are for just an hour or two and the chance that we could re-fill those times on short notice is negligible. Another is that all we're really out is an hour or so of learning how to do our job better...i.e. engineering.
You, on the other hand are booking days at a time and 50% up front is very reasonable. Does this guy not have a credit card?? If you don't take em...get a square pronto. It's easy.
Just as an aside: One client, a local advertising agency, went bust about 15 years ago and left owing me over three thousand semolians. That was a bitter pill. But about three years ago the principals in that agency finally got refunded and restarted a new agency and brought all their business to me because I never beat them up over their debt. A goodly chunk of business I might add...steady...for three years and counting. Plus they are slowly paying their old debt off as well. What goes around does occasionally come around:-)