It's extremely time consuming and so much hard work. 

Inventory is extremely thin.

It is extremely clear that I am a person not a company (some people care about that) and that I'm looking to purchase their home should they wish to sell in the future.I give them every single possible way to contact me, including my home address, my phone number and my email addresses.

If you have time for a quick chat, I can share some additional info you would probably find extremely valuable before proceeding that could influence your investment strategy. 

We've been trying to tackle the smaller projects but have been disappointed so far with schedule and buget overruns.Also, any tips on how to properly vet property management companies?

If you want to look into doing it yourself let me know, we handle almost 600 units in-house except in extreme circumstances and I can show you products and use to handle it.

I am extremely gifted at finding great deals.To start: There is a little 980 sq ft house 3 bed, 1 bath.

Even if you have all your tax-advantaged accounts in Index Funds (a-la Warren Buffet) you're probably going to get around 7% over the course of those 20-30 years, which is a pretty solid return for having zero time invested, and extremely low risk relative to other investments.

It would be extremely rare that any property would not be on the tax rolls. 

First thing, unless we get extremely lucky, we will not sell all four houses at the same time, definitely not within the time frame the IRS requires.