I've been a small time buy and holder investor for about 10-years and am now looking to supercharge this to build both a legacy for my kids one day, as well as a path to exit my W2 job.

You don't need a reason, though it sounds like you have plenty.Do yourself a favor: buy "Every Landlord's Legal Guide" by NOLO.

If the numbers work, buy a place. 

I have 15- 20k and want to buy. 

The lady that bought them down was trying to buy an Island in Clear Lake CA that I had worked on with another developer in the late 70s and it could not be built on at all period.. she had this big dream would never have happened but Remington stole her 10k and she went on the war path..

It took about 2 years and I built a thriving STR business as well as buying and selling houses. 

At what point do I reach out to the homeowner regarding buying the property?

You don't have to have that to get a loan or buy a home, but it will help. 

I used to use spreadsheets, then moved to when QB as my portfolio grew, now on Digb because I have multiple LLC and I don't want to have to buy QB subscription for each.

Rent control is a huge topic to RE buy and hold investors full stop.