Our ultimate goal is to be able to comfortably retire (if we want) in our mid to late 40s.

You determine what to offer by setting goals and knowing your market.

My primary goal is cash flow. 

Here's my advise, Listen to all the BP podcasts and spend a few hours a week reading forums and blogs on here and you should get an idea of what goals will work for you, good luck!

Investing in real estate is something I have always been interested in, but thanks to BiggerPockets, something that seemed like a far off goal now seems attainable.

I second @Ronald Rohde, its a difficult question to answer without knowing your specific goals (for yourself and the property), risk tolerance and local RE market etc.Are you trying to decide between opening up your own business in the second unit or is your list of business the potential tenant pool? 

My goal is to increase rental income so that I can hopefully retire in 5-10 years.

Bring the realtor or investor to your meetings with sellers and learn how to speak with the sellers so that their goals will match your investors.

My goal is to acquire two cash flow properties and potentially complete one flip by next year.

My goal is to have $20k cash in hand by April, and I am currently on track to meet that goal.