Not sure if this will help, and without knowing all of your details, you have a few routes.
20% down is actually nice. This is fairly recent as banks were lending at 25-30% down for RE investments in 2014-2015.
1.) To have a smaller down payment you could consider buying the property as your primary residence and reduce your down payment requirements to >10% DP. The downside is you will need to live in one of the units for 12 months. Again without knowing your situation - this may not be something you are willing to do.
2.) if the seller owns the property free and clear, you may be able to negotiate owner financing for a smaller down payment closer to 10%.
3.) if you have the ability to raise private capital from friends and family, you could purchase the property with cash, use the rents to begin paying back interest only to your private lenders, and after you have a rental history established, you can do a cash out refi with the bank to pay off private lenders. This will ONLY work if you purchase the property with equity in the deal. For example, if you purchase a house worth $100k for $80k cash, you could then bring your deed to the bank and buy it from yourself for an appraised $100k in which they will lend you 80% of the value. The bank gives you $80k at closing and you pay off your private lenders. Your expenses would be any closing expenses and the interest to your private money.
Let me know if this helps.
Ramsey