That's what I need.....Look, I feel for ya I really do so i hope this doesn't come off as too critical, but your desire is a fantasy, and a dangerous one at that. 

Also features that are desirable in duplex would be a separate heating system which allows the duplex part to adjust its heating and air conditioning to whatever the renter wants.

Back then, prices were much better, and turnkey marketers could make a decent fee.As prices increased, many turnkey providers had to move to less desirable areas (I know people are always looking blame other people but in reality blame it on yourself for being the investors that picked bad areas and did not do due-diligence and buy assets where the numbers worked with 10-20% economic vacancy), and now that gap has essentially disappeared.

So they are often not desirable for a primary residence or even a long term rental. 

Some good answers here so far but one I haven't seen yet is desirability.

You can learn from the sponsor on the deals and then go out on your own if you desire or later decide you are happy to keep investing and not put in the work yourself.

If you don't have a firm commitment, how will you handle a less desirable loan?

No thanks they say, visit us where we live, but we have no desire to visit the city. 

I do not really have the desire to buy more unless there is a really good deal that comes along.Some people tell me that if I pay off my mortgage early then I will be able to leverage the tax benefit of owning and paying mortgages properties.

The way I've valued multifamily properties is to calculate the Net Operating Income (Gross Income - Expenses) and then divide by desired cap rate.