Watto,
The cost of the business depends on a lot of factors. Is it running at a profit? What are the expenses like? Will you need a lot of insurance? Where are the machines located? Do they get damaged a lot?
Figures:
What is the ROI you want? What is the risk factor? What about the opportunity cost? Eg: if you can get 7% p/a ROI on a property (in CG) and have neutral cash flow from it, then you would want more than 7% from this business year on year. Add in a risk factor of say 5% and you now need 12%.
Look at the economy. As people start pinching pennies will they still purchase snacks/drinks from vending machines? Or buy things from the supermarket?
With regards to depn it is like a house, you can only claim the portion in that year, so 1/365 for the year's depn in that case.
Is this post/question more of a "I am just mulling it over" type thing or a "I am heavily doing some research and about to buy" venture?
Getting the value from a business can be a very complex thing, and something you should talk to an accountant who specialises in the field. It can be something like 5-7 times the EBITA (established manufacturing businesses for example) or 80% of yearly revenue (an example is a hosting business) so you can see methods vary a lot.
Cheers
Ben
P.S The above advice is of a general nature and is not expected to be relied upon.