@Tiana O. It took me 5 years to get to 10 units.
Year 1 I purchased a 6 unit building in Queens, NYC for 850k. 250k cash (from savings) down + a 15-year conventional fixed-rate loan against my primary residence to purchase it in cash - it was bringing in $6900 in rents at the time. Spent the next two years plus another 200k cash (from savings) re-positioning the building (moving out low paying tenants, renovating, etc.) and have gotten the rents now up to $10,500. Value of the building (six years since purchase) is conservatively now $1.4m
Year 5 - with the 6 unit under my belt and saving, saving, saving from my W2 day job, I partnered up with a buddy and went halfsies on two duplexes out of state (Nashville, TN); 25% down on each, conventional fixed-rate 30 year loans on each. That kind brought me to ten units.
Now in Year 6 I've kept it going and picked up another four units out there with my buddy (14 units), and a duplex on my own (16 units). Definitely feeling the snowball affect with the rental income now - we have enough in the bank account to put down 25% and move on another duplex with maybe only 5-10k each out of pocket to close/renovate.
Goal now is to pick up 6-10 units a year for the next few years.