Hey Jacob!
Congratulations on starting so early! The one thing everyone says they wish they did differently is they wish they started sooner. Congratulations on letting this not be you! I am a realtor in College Station and work primarily with investors. Hopefully, their advice to me will help answer your questions. Every investor goes about investing differently to fit their personal needs and as for your questions here is the best advice I can give you
1. Which comes first, Single Family or Investment: Investors do this both ways depending on which way works better for them. My receptionist almost two years ago bought a quadplex with her Husband using the VA Loan and putting 0% down. They have been living rent-free and just recently bought their first Single Family Home. You can do the same thing using the FHA Loan. Both of them are very frugal and were fine living in and managing a quadplex to live rent-free. If your girlfriend is truly frugal and fine living in a small unit this financially makes the most sense. On the contrary, one of my clients had been renting out one side of a duplex and was ready to get out and into a single-family house that they later turned into a rental property. Talk over the options with your girlfriend and see which option would work best for you!
2. Single-family or Multi-family first: Again both of them have their pros and cons. When deciding this I would focus less on the pros and cons of renting and owning them and more on the loan qualifications you are looking for. My father and I are looking at a duplex to add to our portfolio and when talking to a loan officer about financing they brought to our attention that multi-family homes require a 25% Down Payment using a conventional loan instead of the standard 20% because they are considered "Riskier Investments." Going back to your first question this is another reason my assistant bought a quadplex. They were able to purchase a multifamily home with less than 25% down. You will have to run the numbers to see if it still makes financial sense. As for finding a duplex get in contact with a local realtor that has experience working with investors. They will be able to help you find duplexes were you aren't purchasing only one side. For the Houston area, there is an agent that I would recommend. Let me know if you are interested!
3. Are college areas a good place to start: You are correct that they never have trouble finding tenants. During the 2008 Housing Crash College Station was hardly affected due to College Students having to have a place to live while going to school. With everything going on with Covid right now no one knows what the future holds. There is some discussion on how COVID will change in-person classes and very few people that I know are concerned with the College Station rental market. Even over the past few months with COVID and social distancing the College Station market is still running strong and never missed a beat. ultimately deciding if you want to invest in college towns is down to the pros and cons of college students. Like you said you know the pros and cons of the decision is up to you and your girlfriend.
4. Should you live close-ish to your first investment: You should always manage your first investment yourself and invest in areas that you are familiar with. A lot of people that are in Houston invest in College Station and manage it themselves. 1.5 hours is a decent drive and isn't terribly long if something does come up. Unless your property has a leaking toilet that is flooding your property most everything can wait until a weekend or after a workday to have fixed.
I hope that this helps answer your questions! If you do have any further questions don't hesitate to reach out! You can google my name and find all of my contact information.
