Podio is somewhat complex, but it is very robust and will likely be very useful once set up.

However, I think it would be difficult to build a functional ADU over a garage on that small of a lot since the building form for an ADU has setbacks and building envelopes that would severely limit the building size.

At first, he said everything was functional and livable.

The roof/water heater/HVAC/Appliances/Flooring are all new but, HVAC is not functioning and is not up to code. 

It was built in 2005 so many of the features are outdated but they're functional from the looks of things.

Second, it looks like you are dealing with someone who is legitimately low functioning so tread carefully and document everything.

You aren't "almost/sort" functioning like a real estate agent... 

Lastly, I urge you not to make the mistake of thinking, just because you do the property management yourself, that the expense of that function magically disappears!

I just need some basic functions, tracking rental income and expense categories.

Functionally it is another line item expense that you need to account for in your projects and if two homes rent for the same amount and have roughly the same tenant class and expenses other than taxes, than the taxes will be directly affecting your bottom line of cashflow.On flips it matters less, but is still something to take account for in your budget and make sure that plenty of homebuyers are wanting to buy in the high tax area.