How do you keep track of your rental portfolio?

[Ben Bakhshi]

I have an itch that I need scratched and am thinking of converting an Excel sheet that I use to keep track of our rental portfolio, into a really simple web application that I can share with friends.

It keeps track of:

Purchase Price and Date

Current value (I estimate the values once every 1-3 months)

Loan info (rate, maturity date, amortization)

What I get to see as a result of these inputs:

Chart of total portfolio value

Up to date LTV, which helps me make financing or sale decisions.

Is there anything else you would want to see if I were to give you access to this? 

Is there some service that is already providing this exactly, so I don't have to do it again?

Zillow lets me keep track of values across my portfolio as well, but it doesn't have these subtle yet important features that help me keep track of my portfolio and so I resort to my own Excel table periodically.