Welcome to BP! You can find all the info you need here on this site. I suggest reading the beginners guide here on BP. I am too looking at first investment property as a live in multi unit and I am 23 years old.
1. I am currently reading Investing in Duplexes, triplexes, and quads by larry loftis and I think its great . Here
is the link to amazon:
http://www.amazon.com/gp/aw/d/1419537253?pc_redir=1399678567&robot_redir=1
2. This will be answered in the beginners guide, but I would recommend speaking with lenders and see how much you can afford and then you can go from there.
3. Redfin.com, zillow.com, trulia.com, homes.com, craigslist.org
4. I would suggest figuring out where exactly you want to live since you stated you want to live in your first investment property. For me personally I have family in the west suburbs of Chicago so that is where I am looking for multi family properties. If you want that warm weather almost year round look at Florida and Georgia.
5. Network, research areas, write down goals