For example, say a neighbor refuses to pay rent, then they get eviction filled.

Even soap, let’s say a car detailer as an example.  

I'd say as long as you have $10k after closing for a property that isn't COMPLETELY disheveled with it's most expensive items (roof, HVAC, plumbing, electric, etc..) you can conservatively move forward...Most items can be "bandaided" as you go using this reserve & by following the same principles you followed to get to that $10k + your additional savings and wealth building by buying, you should be able to then take on all the "permanent" fixes within a year or so...

Zoom out to the bigger flippers who are doing 7+ at once-->they've usually got their procedures and systems in place and there's less value to be added compared with the "switching costs" the flipper would view a new manager as.Following this reasoning I'd say a "sweet spot" approach would be to find people who are flipping 8-20 homes each year and get to know all of them. 

Being upfront is generally better telling the land owner you want to sign say a 6 month contract to sell to you.

@Michinori Kaneko a when you say a HEL is like a mortgage, it is a mortgage!

And like ANY 'commodity,' homes that are bought and resold like clockwork ultimately can 10- 100X say a 15- 30 year play, with 3:1 interest, to principal... so it amazes me that ANYONE is still buying, holding and "renting" SFRs, in the 21st Century?!

So I guess you could say a buy and hold strategy to create a portfolio containing the aforementioned.

Meaning it is not say a bunch of buildings surrounded by other property owners like 20 quads on one street etc. 

I think the main issue is that you can easily put,say, a 30amp fuse in a 15amp circuit which defeats the purpose of the fusing and allows you to overload the wiring.