I own the property free and clear and i use the equity as part of my business line of credit.

It’s usually best to open a separate business checking account so your rental income and expenses stay organized and away from personal funds.

The webpage has them based in Maryland but they aren't listed in the state's business directory.

.: Quote from @Chad Hale: I used QB when first starting my property management business.

Try talking to local banks who want to do business with you.

This arrange that you will have will likely be a headache(major assumption on my part).First - Do not do business with a friend. 

I am not sure what type of real estate investing you're considering, but it sounds like, with your family and busy job, you won't have a lot of time to be hands-on or personally involved. 

I also believe that I should also invest is my business.

@Tonio PearceYes you should create a business plan.

I find that it's almost a one stop shop in that I can use it for my business checking and savings accounts, bookkeeping, for rent collection, I can issue virtual credit card, I can create all the financial reports I need to run my real estate business and prepare for tax filing and through their partners I can vet my tenants, develop state-specific leases and more.