I sold my last rental property late last year for two main reasons. One, I needed to reduce stress in my life (renting is not for the faint of heart), and two, my cap rate dropped from 10-11% to 4-5% over the years due to values and property taxes rising at 3-4 times the rent rates. At cap rates that low, the time it takes to run a tight ship just isn't worth it. I can easily make that in the market all day long doing nothing. So, first piece of advice - mind your cap rate! The rising value of the properties was nice when I sold them, but Uncle Sam gets his cut in the end (no more 1031 exchanges.) I had to write a big check in April!
Second piece of advice is figure out your strategy as a landlord. You can concentrate on keeping it rented and just keep warm bodies in there (don't be very selective), or you can be more selective, but be prepared for missing months of rent while you vet candidates. I was in the latter category because I didn't want to deal with deadbeats. I still had a few deadbeats for tenants, but most were not. Deadbeats are a huge drain on your energy. If you rent to stand-up people, you can be reasonable with them, and they'll reciprocate, making your life easier.
The big question, though, is how to find stand-up people. Believe it or not, but by far, the best way was by looking at their credit rating. We found that people with good credit make good tenants, but you have to have a property that is rentable to people with good credit. People with good credit generally don't rent crappy properties in questionable neighborhoods. Unfortunately, we found that it got increasingly difficult to find people with good credit over the 20 years of being a landlord, so our time unrented when up a bit, hurting the cap rates further.
I think there's more money to be made in the lower end of the rental market, but I just saw that as too much work for a side gig when working 60 hours a week.
Find a management company to find and vet tenants. You don't have to have them manage the rental, just find your tenants.
I tried that the last two years of ownership in an attempt to ease my stress, but they didn't just find tenants, they managed the rental. I still did all the repairs and maintenance. They took 9% for that. It was a complete disaster for us. Worst tenants we ever had, and we had issues to deal with way more often. One time, I got called about an electrical outlet that didn't work. When I went to repair it, I noticed the garage ceiling's drywall sagging, so I went up in the attic. They had stuff stacked up on the drywall between the joists (including a full 20 lb propane tank), and it was pulling the nails out. I was surprised it hadn't come down.
I told the management company to inform them to remove the items, fix the drywall, and bill the tenants, and figured my work was done. A few months later, the tenant moved out. In the move-out inspection report I received, there was a ton of damage, and low-and-behold, the garage ceiling was in the report. They never did a thing about it. That tenant was the first in there after a $10,000 remodel. We spent $5,000 repairing all their damage. We ended up keeping their $1,250 deposit, and eating the balance. If the management company had done what I asked, they would have gotten paid prior to the move out, and my loss would have been lower. Fun times! That's why I don't like deadbeats, and that's how my one experiment with paying someone to manage the property went.
My grandpa was so degusted with it, he just gave it to my dad a few months later. I know he seriously considered setting it on fire. 
