Read the forums, read books (maybe a suggestion is The Millionaire Real Estate Investor by Gary Keller) and set a strong foundation for yourself.

And yes it's absolutely vital to read a ton of books, blogs and listen to podcasts every day to continue to grow your knowledge foundation.

Simple build - it is a 2 piece modular house with a concrete foundation, roof only 5 years old. 

We began marketing the property as a fully renovated rental once the foundation for the new addition was poured.

I do agree with @Anthony R. that you need to be sure to include enough in your budget for repairs and also Capital Expenditures (new roof, furnace, etc) I think @Ben Leybovich did a study a while back and found the average home in American needed about $250 in repairs per month if you really figure in everything that will eventually wear out (the entire home accept the foundation and framing).

In fact, in my opinion, it's your foundation and your safety net that allows you to wait out any market shifts.

If the development provides an ideal enough foundation and surface area for solar panels, between ITC solar tax credit, federal bonus deprecation, and state MACRS deprecation over 60% of the solar investment can be subsidized.

Plus, it's a lot cheaper to build by buying a new manufactured home and putting it on a permanent foundation.

It's an SFR, roughly 100 years old, with a foundation that is in bad shape.

You guys have a solid foundation and it seems like you're well on your way to building an empire.