Admittedly, and I have a biased opinion here being a licensed loan officer in WA state, but I would suggest trying to find a licensed loan officer with some knowledge or experience with rental property owners and investors and pick up his or her brain. As well you want to find a real estate broker who has a focus on investment properties. Again, pick their brains.
I found that Brendan Turner on this site is a very valuable resource for buy-and-hold investors and the book "the ABCs of real estate investing" by Ken McElroy to be another excellent resource in general.
It wouldn't hurt also to go to a couple of property management companies and see what information or literature they can provide you. Sometimes, they'll offer seminars and workshops for people interested in rental properties as a means to advertise services.
Surprisingly, YouTube also has a decent amount of information so long as you can sort through the "guru" stuff.