Hi @Changseok Kim Welcome to the investing community! Your situation sounds pretty similar to mine. We had some equity in our house and opened a HELOC in 2016 for investing purposes. We're now up four houses so the HELOC was definitely the way to go for us. We only use it for down payments and major repairs (that our reserves from rent won't cover).
All four of our houses are located near WMU. I love the older homes and working with the college kids so its perfect for me.
Do you plan to landlord your first property yourself? If you aren't house hacking, then I'd personally recommend a small SFH to get your landlording feet wet. It simplifies the learning curve as you build up a contractor team, figure out a rental software, get a grasp on tracking expenses, etc.
The MFH market in Kalamazoo is really tough. From what I've seen, if a property gets to MLS then its either overpriced or in terrible condition.
If you have any questions, then feel free to reach out directly. Good luck with everything!