As a general rule (there are exceptions), most of these "infomercial gurus" are fast-talking hucksters. Several, like Russ Dalbey, John Beck and John Alexander have been sued by the Federal Trade Commission. A few have even ended up in jail. And several, like Robert G Allen and Albert Lowry have filed bankruptcy at one time or another.
But there is a good real estate investor training course or two available.
One of the better ones is offered by Carlton Sheets. But don't jump just yet. While Mr. Sheets promotes legitimate methods, his course is mighty shy on enough detail to actually put it to use. And there is a purpose behind the lack of detail - Mr. Sheets wants you to buy into his expensive coaching.
This is true with all the gurus (except for "The Simple Man's Guide to Real Estate", the only real estate course to include free coaching). The main difference between Carlton Sheets and most of the other infomercial gurus lies in the simple fact that Sheets actually teaches legitimate (though limited) methods. Many of the gurus pimp methods that are nothing more than snake oil.
Of the Toip 20 gurus, Carlton Sheets rates about #3.