I would start with bookkeeping for dummies. Learn how to potentially keep your own books. It should start to make a little bit more sense how a profit and loss statement and balance sheet tie together. I have not read or used this book so I am sure there are other choices.
I am still thinking about your offer. I could use some cooking lessons (according to my wife) and I am a 16 year CPA Australian qualified accountant.
I am hoping a job comes through soon which will give me less free time but like the other poster if you get stuck I would be more than happy to answer any questions online.
After bookkeeping you could advance to some more accounting but the debits and credits are the building blocks.
Funnily enough your question on how much cash a business should keep I don`t think has ever been answered in any theory I`ve studied. I`m assuming you are actually talking about how much change you would need on a daily basis? Which would depend on type of business, how many customers per day/ no of transactions etc. Answer, just carry lots as having extra coins on hand isn't going to hurt your overall balance. I am sure a little experience and you would work that out yourself.
Otherwise, if you are talking how much cash to sustain/ start the business. The more cash you have the longer you have to build a positive cash flow generating business. You would make a plan and I would say be a pessimistic at the start in terms of how much income you get and see how long the cash will last and then you have to decide if that`s a risk you`re prepared to take.