There have been businesses on the forums talking about such a business model, even offering some tech support and more, saying that having equipment on hand that is paid for justifies the plan. One such model I remember had a person on-site during the event as well, and if I remember correctly I got into a discussion about doubting the potential for making money even at $500 - especially if service beyond lending the camera, dj equipment or whatever included a person on-site, or further services following the gig.
I try to base ALL my work on a minimum of $70 per hour, even though some of my work is priced turnkey, or packaged. I have still honed whatever production requirements any given project may call for to the point that I can average $70 (often more) per hour, satisfying my hourly rate needs for a viable ongoing profitable business.
Most equipment rentals are going to run in the range you are considering, and that negates ANYTHING else done that takes time or money. TIME being money, you need to realize that just because you're busy, and doing something for pay, doesn't mean you are making money, much less a profit.
The ONLY way to ensure that your efforts are paying your way is to honestly add up EVERY possible expense your business operation incurs - gas, pencils, tapes, equipment, upkeep, insurance, meetings, and the ACTUAL and REAL time it takes to output any given project - add, subtract, multiply and divide and come up with what your hours of work require to cover ALL expenses and money invested. Most of us are operating at a loss in spite of our best efforts when the realities are taken into consideration. That doesn't mean we're stupid or not educated, it just means there are other "emotional" or "personal" factors that come into play.
In the end, however, if anything you do consistently means you are operating at a loss you will need to find alternate financial resources to keep your video business going. Otherwise, you are throwing away your money and your life where both could be better spent improving the way you live by pursuing another course of action.
Somebody once told me that being a journalist or being a video producer is like getting married - you'd better be in LOVE and take particular notice of that part about for better or worse. ;-)
ON THE OTHER HAND - having a low priced leader that brings clients in so you can up-sell services, enhanced projects etc. is a GOOD business plan provided you DO find ways to increase the income for the time spent. Good luck. If you stick with looking at practical but profitable ways to produce and make money at a reasonable rate you will come out on TOP.