I am interested in recommendations for online courses or books (or other sources of information) that people have found useful. 

There are some crime maps available online too.

We do cold calls, online marketing and sometimes even door knocking to find motivated sellers.

I would not go online to get medical or legal advice from randoms. 

I just use an online platform to collect rents automatically. 

Here's where to look for them:Real Estate Investment Groups and Forums: Participate in social media and online forums devoted to investing in real estate in Houston and its surrounding areas.

Do a search online, make some calls, choose one, and prepare for the long fight.

Try alternative ways of contacting them like finding out who owns the property, going to meetups, or seeing if they're any online groups for airbnb owners in your area, like an FB group or something.

The "old dogs" there keep their mouths shut unless it is to ask for money.My advice is to run from that program, and invest that money is online education, on well known resources such as the Kent Clothier reww system, this Biggerpockets forum, the cheap and inexpensive marketing programs from John Cochran, Chris Prefontaine or many others that will help you to get started without having to spend tens of thousands of dollars on mentoring of people as little genuine as the Groves.In summary, Phil Grove's program will not work for 95% of the people that enroll on it, and out of the other 5%, it will mostly help those that end up in Phil's team.

There are lots of basic calculators online, including right here under the 'tool' tab at the top to help run numbers to see if the deal makes sense.