Things I wish were stressed to me when I first started out include the following:
1) The importance of using conservative numbers with cash flow and building up considerable savings. One repair such as a crack in the cast iron pipe under a lawn can cost a few thousand, add in reparing a roof, etc cost add up faster than you can breath. I found the only buffer was considerable savings and having good people easily accessible who could help out.
2) I would take time to really understand how safe the neighbors truly are and the types of crimes too. Sometimes the real estate agents honestly does not know this information. And if you plan on living in the property, wouldn't you want to know? Also, if you are getting your real estate license (agent or brokers) you will want to distinguish your services from everyone elses.
3) As for researching individual properties for yourself to buy for income, the number one thing I would say is build up a huge network to support you. Perhaps you are already skilled in repairs, maybe you are not (yet). Regardless unlike others I do not advocate being a jack of all trades, mastery a few and surround yourself with people who fill in your gaps.
For investment properties I found since my first purchase I wanted to ease my burdens, minimize costs, while increasing time & effort efficiencies whenever possible. So as much as possible be patient with yourself and the market while building up your team of people who can help you (licensed contractors, local utilities, lawyers, financing, and building inspectors). I use to spend most nights and weekends studying the markets I was considering (visiting them during random times to study the neighbors, schools, crime, and resources).
These are three main ideas I wish I practiced early and I recommend doing the same if you really want to understand new areas and bringing greater value to your prospective buyers/renters. Good luck! Cheers!