I bought my first rental when I was in grad school in Colorado. I was 27 and bought a 4 bed/2 bath for 182K in 2007. I worked for 2 years in between undergrad and grad school to save the money (2002-2004). I didn't make much money, but I lived at home for free and saved enough for a down payment. I also used a tiny bit of student loan money to make it work.
The total mortgage, taxes and insurance was $1040 and the rent from renting out 3 bedrooms was $1050. I refinanced 2 years later because rates dropped from 6% to 4.75% and my mortgage dropped to $950. I lived there for 4 years. For my 5th year, I moved to Florida for a job. My roommates still wanted to live at the house, so they found someone to rent my room. One year later, I started renting to random college students on craigslist. I'm now renting it for $2,000/month. I'm also turning it into a 5 bedroom for next year and going to ask for $2200-$2300/month.
For my second rental home, I also purchased as a primary residence in January 2012. It was a 3 bed/2 bath single family for 95K. I was able to come up with a down payment only after 6 months of working my first real job, because I was living at home again. My dad had purchased a vacation/retirement home in 2006 that was in the same town as my first job in 2011. I lived there for 6 months and had 15K for a down payment and closing costs. I started renting that house out in August 2015 because I got a better job in Hawaii. The mortgage, taxes and insurance is $650/month. I rent it for $1700/month.
I'm hoping to make my 3rd purchase in Hawaii within the next 12 months. I'm looking to buy a 3 bed/2 bath house, with a 1 bed/1 bath attached studio (ADU). The ADU will get about $1,100/month in rent. I'm looking at purchasing a house in the 300K-500K range. With 20% down, that will put my total mortgage in the $1,350-$2,100/month range. However, that will be off-set by $1,100/month in rental income from the ADU.
I'm thinking of refinancing my Colorado house and pulling out $110,000, so I can put 20% down. However, I haven't decided yet. If I don't do that, I'm looking at putting down 5% and having to wait 2 years, instead of 1 for a house purchase here.