I read that one person had a $1M policy, but not sure how much that would cost.Yes, umbrella policies are highly recommended as they only cost a few hundred dollars per year on average.

I work with @Joe Homs and focus on the Newport Beach and Costa Mesa area. 

Well thank you - I am going to take your advice and paint the floors - I think it will look nice and not cost a whole lot.I will also have someone take a look at the foundation - that way if they do need to jack it up a bit - I can paint the walls AFTER they've potentially shifted or something.My main weakness is that I hate bugs and am horrified at the thought of crawling under the house.

@Costa DeirHey Costa, that is exactly right.BRRR strategy is mentioned many times on BP, however it seems perhaps many on this thread are understanding this concept. 

But I live in Europe, so mailing out targeted fliers to people would be crazy expensive unless I paid someone to do it for me from there, but that’s another cost as well.

You 100% will have one or two things happen each year that cost a grand here and there so your cash flow is gone. 

Flipping properties can still be a valid method I would just be much more choosey on properties that you have because you are going to want to budget for holding the property for longer than you think which can cost a lot more money to do.

That's now double the cost. A

A really good GC is going to cost a lot of money.

Adding central heat and Air to a 12 unit could cost a lot of money and be very disruptive to your tenants unless duct work is already running through the walls.