Hey @Theodor Kim!
First off, congrats on your personal journey with REI. I'm semi new to REI investing and started reading and listening to Bigger pockets 2017, didn't pull the trigger until April 2019 to get my first SFH. I'm currently closing on a duplex that I will rehab and get rented out too in Gainesville FL.
Since your goal is to have a multi family, acquiring a triplex or fourplex, an FHA loan with just 3.5% down will help a lot. You can even investigate the 203K loan within it to help with your rehab and wrap it in your loan, if the numbers work for you. Just keep in mind the additional Private mortgage insurance, you'd need to refinance your loan in order to get the PMI out. This is also beneficial if you needed to do some light rehab anyway. You'd get chance at another appraisal and hopefully some loan pay down from your tenants that help reach 20% equity to get that PMI out.
I know some banks, depending on your credit score, will offer their version of the FHA loan requiring 3% down. Might be advantageous for you if you don't want to refinance your loan since there product allows for the PMI to drop once you hit 20% equity. These are great options for someone to get a primary residence loan to afford a multifamily house. Just make sure you crunch the numbers and add all the fees. Remember you must pay fees (closing costs) and some points, depending on your bank, when you refinance. Just keep that I mind. My lender told me to calculate 4-5% of asking price for your home for closing costs.
I would also figure out my target price ranges for these SFHs or MFHs. Then figure out the rent that will come in. Once your have those numbers it should be easier filtering through sites like Zillow. You can also find a property manager and ask them how much they would rent those units for, to get accurate numbers.
Hopefully this helps! Sometimes you just need to find a decent deal first and work it through before things start clicking. Use it as training wheels that will prepare you for the next one.