Go to the menu on the right hand side of the page, and select the "Real Estate Investing" topic, and then when that expands you will see a topic called "Investor Basics".

There are tons of good materials under Education menu of BP.

It seems like you may be considering a new direction for your flipping business and I think you'll find one of the resources available from this site most helpful in that respect - 'The book on flipping houses' from the menu above. 

Under the TOOLS menu along the top there is both a Flipping Calculator and a Rental Calculator.  

So if you're semi retired then I'd suggest a semi passive more surgical approach from the following menu (believe me if I could mix any more metaphors here I would) . or mix n match. 

Take a look at the rental property calculator under the tools menu, there is also a ton of information about it in the blogs.

You can also try the Biggerpockets calculators for rental properties, they give you some pretty nice graphs and help you with cost calculations (see them in Tools menu).

@Bill Briscoe look in this next link: http://www.biggerpockets.com/real-estate-forms.html You can find that link under the "Resources" menu at the top of this page, then choosing "REI Resources" from there!

On the left box labeled "Document Type", pull the menu down and select "proposed rules" 2.

Maybe as a dropdown menu for each option along the "toolbar" that goes along the top of each page?