I think the biggest "?"

The biggest keys are:1 - The design should have the least amount of waste. 

I love that you rented two of your bedrooms as mid term and short term rentals and made enough to pay for the mortgage and now you are going to use the rental income to show you can qualify for another property.This is an excellent strategy and one more people should consider doing in this inflationary environment to offset the biggest cost in their budget--housing.As you rightly point out, you can use this strategy with every house you buy accumulating a portfolio of houses that you originally started out living in as a primary residence every two years.Well done and more people should consider doing the same, or rent their garage, or shed, or a boat, or an extra car.Love it!

I would take a hard look at each one of these areas to determine where the biggest problem is, and then fix it.

My biggest issues so far is that they have had some labor issues on the maintenance staff but this is everywhere and i believe will work itself out in the coming months. 

Other than institutional lenders turning off the spigots in May of 2007, our single biggest exposure and source of most of our problems was the quality of the property management.  

Cost alone not being my biggest consideration.

so realtor biggest cost is "tech cost" , quite similar to "medical sector".

I said it 10 years ago when I was on the BP podcast, and it remains true today....the biggest mistake investors make is an inability to properly judge risk.

However, the biggest challenge is dealing with well and septic systems, which can cost $15K - $75K to fix.