The best way is to build a relationship with a local realtor who will sit with you and establish rules of what to look for when doing comps for you.If they know you are serious, and they are too, then they should be happy to help you.

In my locality, with an occupant we want out, that isn't paying rent and the status of a lease is unknown, I've only had to establish tenancy and demand a rent amount in a letter by certified mail. 

Not established people with “options” who wake up and figure out that they should be paying off a note not their landlords note.

With flips it isn't really an issue, but BRRRRs we would need to have it established from the start.  

But it is important to establish yourself in one area before diving into others to ensure that you are as focused as possible on generating great returns on that specific strategy. 

That the established players have the old way and it works well for them given they have already built a network of investors.That new operators, who used to have to use the 'old way', will migrate to the crowdfunding model (SEC definition)?

The Simple Path to Wealth by JL CollinsThis is by no means an exhaustive list but is a good overview of some books I found helpful in establishing some of the foundations for real estate investing and money management.

yes since they've established tenancy, even with squatters it's the same thing. get in touch with the sheriff's office if you need help or have questions about this. do it the legal way at the courthouse. i'd recommend getting an attorney 

Also, if you need to get a financing, and have a long time established credit, it should be easier for you than for someone younger starting out in life to obtain a loan. 

In DC, you can't GC at all without a license.Also, I wouldn't say that GC'ing yourself will be cheaper--in many cases, since established GC's have longstanding relationships with subcontractors and suppliers, they can actually provide you cost savings over performing the project yourself.