Commercial loans are much different than residential mortgages. The 8% is just a number I typically use as a baseline for initial calculations. With the prime at 8.25% - you could be looking at something around 11%. If you can find someone to lend at 6% today - you`ve got a good deal.
If you are going to purchase this business without any capital of your own - you will need to find a creative approach to financing it.
Typically “the cost of capital” using creative financing is greater and therefore you will need to “show” how the business will be able to provide a rational risk-return to the parties who supply the capital.