I have 3 rentals and while I have been lucky with my tenants being long term and overall great.... most aren't. I know one friend that owns a rental in the same condo that I have one of mine in and he has been stuck with a tenant he can't get rid of for 16 months now. 16 months without being paid a penny. That is 16 months he has had to pay the HOA fees there and infraction penalties and/or damage that his tenant incurs. Once they become squatters, it is a big mess and they never take care of anything once they stop paying. You can use the courts to evict them, but that is money out of your own pockets you will never get back and then the money you have to spend to fix whatever they fucked up out spite before they were escorted out by the sheriff so to speak.
Rentals are a great way to supplement your income, but unless you own dozens, you won't be able to make a living off of them most of the times.
Buy and rent out in a rural College town, it's stupid easy, but you have to be flexible. My best housing returns are in College towns, find some houses near the campus. I've sold a few of my properties in Houston just so i can invest more into my three rentals in College Station, Texas. I'm renting houses out to rich college parents for $2800 a month that should fetch around $1500; within 10-15 years they will have paid themselves off. You just have to be prepared for turnover, but each semester i have a "list" to pick from. Just don't get mad when they break something.

Back to the topic. This is why you get a real degree. Hell my first job straight out of college as a structural engineer made me 48k a year in 1998. Within 10 years i was making around 75k i think and getting nice bonuses. I pay engineers straight out of a "good" college program around 55k. If they bust their ass for 4-5 years and get licensed, i'll bump them up to 70k no problem.
Kids today do not understand money, they will buy a 60k BMW, 200k house and 50k wedding within 5 years of getting out of college. But they won't pay anything more than the minimum on their tuition debt because they are retarded. I paid off over 50k in loans within 5 years of graduation. Cry me a river. I also worked 20-30 hours a week the entire time i was in College.
Like others said, be smart with money, don't buy stupid things you can't afford, pack your lunch, only buy clothes and other items on sale, buy the off brand items at the store. If you live like this for 5-10 years and save money, you will be in a good place. But most people believe in instant gratification, they have to have expensive clothes, cars, TV's, etc. I understand, but there is a smart way to manage your money.