It's easy to open bank and credit accounts. Harder to close them permanently and to track all the activity in each one. Especially transfers to and from the different accounts.
With today's money management systems (and there are lot out there), it is easy to track these transfers without getting confused. The most important thing is to have a system where all the activity is captured. If you can't track the ins and out, then it can get very confusing and transfers from one account to another could be mistakenly booked as income or as an expense.
All of my clients manage business, household, and personal finances. In addition, the bank and credit accounts are usually held with five to ten different financial institutions ranging from large banks to small credit unions. The first step I take when I help a new client set up their Mint is get a complete list of all of their accounts. Then, for each institution, we see if we can import the transaction activity into whatever money management system they have chosen (I prefer QuickBooks Online, however it works the same for Quicken, Xero, Sage, Mint.com, etc.). It's important to have every account import directly into your system. This will drastically cut down on your time and money errors which will not be caught by you or your tax accountant until usually it is too late. Everyday more and more financial institutions are making sure your data can be imported. If your bank doesn't import directly, it is easy to download the activity and then import it into your money management system.
What's always eye-opening when I do the first initial import with my client is the cost of some of these accounts. It could be a credit card opened to achieve a discount on a major purpose, only to have additional fees (such as annual membership dues) tacked on. It also shows clearly all those small recurring subscription fees. One client was paying $34.95/month for many many years for something she could not even remember what she used the service for and had assumed it was part of her telephone service. After she saw everything in one place, we researched the charge only to find out it was for a powerful computer anti-virus/identity theft service she had purchased years ago for a computer she no longer used. Because she was so busy, she didn't pay attention until she began managing her Mint each week and realized she had paid over $1,250 for something she had used for less than a year.
This is what a Mint does for you -- it provides feedback on where your money is going and what it is being used towards as well as how your money is being received. If you have clients that pay you using credit or debit cards, then you know those transaction fees can really add up. This doesn't mean you stop accepting credit or debit cards, rather you are better able to assess the cost and look for alternative services that may be less expensive or adjust your prices accordingly.
Finally, we all have multiple debit and credit cards. Some for personal accounts and some for business accounts. It's easy to say, "I'll only use this card for business purposes" and then purchase something for your business that is drafted from a personal account. By having everything import, you can code and capture these charges easily, giving you an accurate reflection of your entire money flow.