I've done exactly that before, and more than once I'm afraid. I probably shouldn't even tell these stories...
Kids: DON'T TRY THIS AT HOME (or anywhere else).
One was a double-header Pro-Am at Carolina Dragway. After being on the road for several weeks, I came home to realize I had forgotten my truck payment. I paid two months on that to catch up, and after paying the first day's entry fee and Jill's crew ticket for the weekend, I had like $16 in my checking account (and more bills due in the next week). I was R/U Saturday night, and they paid in cash. "Hey, we're racing tomorrow!" I bought Sunday's tech card, and won the second race. "...and we're paying the bills!"
Another one was the first weekend out on a fresh motor. Wish list: Piedmont Pro-Am, race fuel, Pageland points race. I only had enough cash for two out of the three. Some idiot
told me "Just write a check, win the race, and then deposit the winnings. It'll cover the check!" Wrote a check for the Pro-Am entry, paid cash for everything else. Made my two qualifying runs at Piedmont, loaded up and drove to South Carolina for the bracket race, R/U there, came back to Piedmont the next day and won the Pro-Am.
Both instances were pretty stupid things to do, but as some cranky old coot (he knows who he is) told me once, "I'd sell my spare tire for gas to get home."
Again, those are extreme and stupid examples, BUT the point is, there are people out there that aren't sittin' pretty in life, but have the will and desire to compete. If you think back, maybe a lot of you used to BE that guy. If a guy only has the money to only run one race, and that's what he wants to do, there's no reason to dissuade him.
You have tech, you have wristbands, you have credit cards, you have open checks, there's any number of possible ways to have a checksum to handle single-day entries. H*ll, you can hold his driver's license.