Advise on Accounting Software
I would say that TioLive would be a good solution for you. It enables you to track your spending and profit, to create invoices for your customers and suppliers, to manage your inventory, and many other features that can be used only in the case that you would need them.
Moreover I'm quite sure that you could manage your business on TioLive free version without any problem. You would just have to register (also for free).