$10,000 for a turnkey business can be a good deal it depends of course on what you get for the money. Even if it is true that $500 a day in sales is a slow day (be sure you see the owner's "books" and tax reports), you need to put that $500 into perspective.

You need to figure your expenses against those sales figures. If your expenses are $300 a day (supplies, rent, payroll, taxes, loan, etc) and you make $500 a day is that an acceptable profit for you? Was the current owner turning a profit? If he's making so much money why is he selling?

Do you have experience in this field? Will the training provided be enough? I assume this isn't a franchise so what if you need further training or direction? Are you on your own?

Keep researching until you're satisfied you have enough information to make an informed decision.

And don't forget your business plan! If you need to go for financing you need a business plan.