I see no one else has answered you, so I will, but I can only tell you from my limited experience. Mostly, I recommend you listen to the podcasts and watch the videos on here as well as read books. They will be able to tell you far more than I can. I have a financial planner who guides me through my decisions.
I strictly do buy and hold, so that's all I can recommend from experience. I'm terrible at being the bad guy, so I use a property manager. I know, I'm not able to give you info on the best way to do things. lol But for me, this is the best way because if I can't evict a tenant, then I'm in trouble. Not to mention, I'm not even good about collecting rent on time. Plus, I'm pretty disorganized. I learned from experience and hired an expert. lol
So, all that being said, I tend to lean towards property that is already being used as rentals as that way I can find out their rental history and have a good idea if they will be rentable and for how much. I have 2 duplexes I bought and they had a great rental history. I got them about 8 years ago and they never spend more than a week or so vacant, if that. They've been great!
I have what was my primary residence as well. One thing I can tell you is not to buy a "down house" (a house where the property slants towards the house). My mom told me not to as our home was also a down house and my parents were always fighting foundation problems (due to water). I bought a down house and have spent the whole time fighting water. DON'T DO IT!
Be sure to check out the area before even looking at the property to save yourself time and to protect from falling in love with something you shouldn't. I refuse to buy in high crime areas, so I check Trulia, though I hear there are better ways. lol I've also asked the police department what their opinion was when I was looking at an area I wasn't familiar with. I've done the same with the Chamber of Commerce. But if you already know the area, that's probably not necessary.
There are some worksheets on here to help you decide if something will be cash flow positive, and if so, how much. But if you're just a free member, you can only use them 5 times. Though I'm sure there are other sites around the internet that do the same thing.
This is obvious, but be sure to get a home inspection so you know what you are getting into and can hopefully get the sellers to pay for some of the issues.
If you decide to use property managers, research first. I got mine on the recommendation of a family friend. While they are the cheapest in town and they haven't done me wrong, they certainly aren't the best. I need to stay on them to ensure things like repairs are done. It took me asking 4 times over 5 years to get a simple mailbox replaced. Also, whether you live in the area or not, I suggest checking on the properties, inside and out, at least once a year. This is how I found out one of the mail boxes was rusting out and the door was off it. The tenant apparently hadn't complained and the property managers hadn't noticed (or cared). (Why do I keep them? Like I said, I'm terrible at being the bad guy! Not to mention, the mom of one of my high school friends is my manager. Doh!)
If you have a tendency to make rash decisions, bring someone who is level headed with you. I also have a time-line, myself. I see the property several times and take 2 weeks to make a decision. That way I know for sure it's what I want. But I know in some areas, this isn't possible. Also, if it's a real steal, that wouldn't work, either. I've only lost one property this way (and I do regret it), but for me, it's worth the chance of losing it. In the time I thought or re-looked at places, I decided against them, so it's saved me, personally. But you know yourself and know what's best for you.
I also recommend starting out just looking to get a feel for what's out there. Don't buy the 1st house you see or buy in the 1st week. Chances are, you aren't going to find a real winner right off the bat. And even if you miss out, there are others out there. Use this time to practice on your worksheets and get an idea for what's a really good deal and what's just a deal.
I think this is all the wisdom I have. GOOD LUCK!