A market open for ignorant $, will abuse and neglect the vast majority of it.

Build a trusted network around you who can act as your sounding board and disregard the vast majority of opinions elsewhere. 

But I think the vast majority of us looking at duplexes / this are doing it for rental income and not so much flipping/the sale.

My experience is that warranties aren't really that good due to the vast amount of exclusions.Additionally, the math may just not add up.

I'd highly recommend visiting the Mises Institute and their vast library on their website. 

I wish developers had more of an incentive to provide housing for the vast majority of people, not the wealthy.

So, it turns out that the real service provided by the gurus is weeding out the vast majority of people that fail and give up from the small minority that fail and don’t give up; instead those seek out REAL real estate and investment knowledge and try again.  

Always Have Financing Lined UpThe vast majority of investors will be financing their properties (and I don't see a reason not to while you're growing your portfolio).

So for vast majority of the history where USA enjoyed position as net exporter, innovator, world currency standard, it was NOT a title held due exclusively to the USA "greatness" as we are all force feed.     

Many OOS investors set themselves up for failure because they don't truly take the time to understand:1) The Class of the NEIGHBORHOOD they are buying in - which is relative to the overall area.2) The Class of the PROPERTY they are buying - which is relative to the overall area.3) The Class of the TENANT POOL the Neighborhood & Property will attract - which is relative to the overall area.4) The Class of the CONTRACTORS that will work on their Property, given the Neighborhood location - which is relative to the overall area.5) The Class of the PROPERTY MANAGEMENT COMPANIES (PMC) that will manage their Property, given the Neighborhood location and the Tenants it will attract - which is relative to the overall area.6) That OOS property Class rankings are usually vastly different than the local market they live in.7) That a Class X NEIGHBORHOOD will have mostly Class X PROPERTIES, which will only attract Class X TENANTS, CONTRACTORS AND PMCs and deliver Class X RESULTS.8) Class A is relatively easy to manage, can even be DIY remote managed from another state.9) Class B usually also okay, but needs more attention from owner and/or PMC10) Class C can be relatively successful with a great PMC (do NOT hire the cheapest!)