number one its going to cost you more then 1500 just to rent it. then figure trucking will be at least another 800 if not more.
and a d8 would have that done in no more then 5 hours anyways. dont you run big iron? you should know a machine like that is just sheer overkill. If you want to do it with a dozer a 450 deere or a d4 cat is plenty big and you can move it with your truck if you wana be a tad risky.
Back to HIS original idea..... he wants to BUY a machine that he can dig the pond with and also use for his biz. A mini is more then practical to dig such a little pond. especially when he has a little dump truck to run with it.
would i rent a mini to do it? NO would i buy a mini and do it? yes because i will keep using it for the biz.