
I documented all of the Treo's calculators in my TreoCentral series on them. To get the information, since there aren't any manuals to refer to, I resorted to poring through manuals for several Texas Instruments models. Theirs had the same functions and many behaved the same way, or were sufficiently similar that I could figure out how the Treo ones worked. I also imposed on a statistics professor friend to tutor me on the Statistics, Math, and Trig calcs and help me figure out how to operate them  over the phone, no less.
A Palm software engineer clued me in on a rudimentary manual distributed with a shareware calculator app on which the Treo's version is based, and of which it's approximately a subset. This gave me much of the information for documenting the Logic calculator.
There's more info about all of this in the articles:
http://treocentral.com/content/Stories/8491.htm (Part 1, a general discussion, inclluding elements common to all of the calcs)
http://treocentral.com/content/Stories/8601.htm (Part 2, documenting the first three individual calculators in order). Note that in Part 3, I corrected a typo I made in the Finance one.
http://treocentral.com/content/Stories/8711.htm (Part 3, documenting the last two calculators  Statistics and Logic  plus the units converters)
The link to the original app, which is still available but no longer supported is in Part 2. http://kb.palm.com/SRVS/CGIBIN/WEBC...m_External2001
For real estate, you're probably most interested in the finance calculator, which can perform useful functions like Future Value of Money (and payment calculation) and mortgage amortization. Other, more complete financial calculators are available as addons. Try this search in TreoCentral's Software tab:
http://www.mobihand.com/treocentral/...1&sString=calc
These cost money, but they add many useful features.
Jay


