However, with increased popularity comes increased competition.

Some of the most popular markets are as follows.ClevelandToledoIndyKC

Section 8 is more popular on the low end here due to the guaranteed income and the HA being more willing to work with us on problem tenants.  

I've found the contrary to be more popular.

Unlike many of the popular cash flow markets, they have solid population growth, job growth and diverse, modern industries.

For free content:Khang Le (Youtube)The Flip Man (Youtube)For paid content:Wholesaling IncPaying for a course/mentor isn't a popular stance here on BP, after all, everything you need to get started, you can find out on your own for free.But Wholesaling Inc holds your hand throughout, lays out a plan and provides you with a community.If you have more money than time, go the paid course route.On the other hand, everything you need to get started is on here (and Youtube) for free!

Obviously my delayed finance process has been popularized for good reason (fannie mae cash-out refi with no seasoning)Also, recently I bought a 24 unit apartment and wanted to bring outside investors in as a JV but I didn't want them to have to take on guarantor liability.

In no particular order I have listed some of the most popular markets for out of state investorsCleveland, OhioDayton, OhioToledo, OhioYoungstown, OhioCincinnati, OhioMemphis, TennesseeBirmingham, AlabamaHuntsville, AlabamaKansas City, MissouriSaint Louis, MissouriIndianapolis, IndianaDetroit, MichiganErie, PennsylvaniaLouisville, KentuckyMilwaukee, WisconsinJackson, MississippiEach of these markets is popular with turnkey investors because of the low barrier to entry, high rental demand & high rent to price ratio.

Their ideas appear to be gaining in popularity. 

You are not restricted to only creating one in your state or the property which is why states that offer anonymity & other attractive tax benefits are so popular with real estate investors.