@Gabi NA Welcome to BP! You're probably overwhelmed with questions but rest assured you came to the right place. The forums and search [box] is a free REI education. Leverage it and learn. Pick up the book Building Wealth One House at a Time by John Schaub. It's chalked full of information, calculations, and advice. No fluff.
1. Yes, most lenders will require you to live in a primary residence before moving out, refinancing, or converting into a rental. Do most investor do this? Yes/no, it's not like lenders do inspections but I encourage you live there, learn, and follow the guidelines of your loan.
2. Speaking of loans... how much $$$ do you have liquid, what's your budget, and what neighborhoods do you want to buy in? Location, location, location. This affects which strategy you could pursue. STR and MTR are basically full time jobs when you're booked. This requires in demand tourist areas. These locations are expensive. Can you make more $$$? Sure. If you're going to school FT do you want to manage this property? Think about the value of your time. A house-hack or LTR makes more sense because it's not stressful and you can focus on school.
3. Rental arbitrage was hyped up when money was cheap. It's basically dead in most areas. You should research it and establish your own opinions but as a new investor it's a lot of work. Arbitrage does not reward the pillars that OWNING RE does.
The best you can do research your market, improve personal budgeting, improve credit, and get your dollars working for you. Have two years of W2 income, RE goals, and start talking to lenders about getting pre-approved. Go from there. Everything else comes from networking, experience, and getting your hands dirty.