First DON'T TAKE 'ANY' ADVICE. That's my advice, take it or leave it. There is advice that is good, and there is advice that will get you in trouble. There is advice that will work for you, and there is advice that will work for other people but would cost you a lot of time and money. Everyone has a different skill set, so be careful with any advice you get. The first advice I got cost me 60k in the long run.
So addressing your questions, here's some more advice. On a limited income.... go buy a duplex and move into it. If you can swing a 4plex, that would get you up and running faster, but there are two reasons you might not want a 4plex. You'll be dealing with a slightly different class of tenants because it's a 4plex. You'll also be dealing with a different class of tenants because you'll only be able to afford a 4plex in a worse neighborhood.... I'd rather have an awesome duplex in a great neighborhood than a 4plex in a slum.... if I didn't have any management experience.
So: Go to a lender, get pre-approved for a multi-family residential owner occupied loan. Save up the 3% or whatever you need as a downpayment (or ask for a gift from family members that want to see you get ahead), and make an offer that has the seller cover your closing costs. Just do a little research till you are confident that the duplex will make money if you moved out.
I would do this even if you live in your own home now. If that home would make money when you move into the duplex, keep it... if not, sell it.
There, that's my advice for someone starting out with limited resources. It has worked for me, as well as many others.