Refinancing is going to cost a few thousand.
The rest is sort of chocolate or vanilla. You can keep doing owner occupied, as long as you occupy for at least 12 months, and have low down and low interest rates. If you are OK about moving, that's a way to keep on going without the bigger down payments.
Let's fast forward to your next few investment properties. The conventional financing rules have been 20% down on mortgages 1-6 and 25% down on properties 7, 8, 9 and 10. You also will need reserves, which is PITI and HOA payments for the investment properties, for six months.
So how to keep going? Fill up the first "easy" 10 investment mortgages, and then move to portfolio lenders. Or find private money. Or buy with owner finance, either the entire loan or seller carry-back.
I like to begin, with the end in mind. What are your goals? It is easy to burn through downpayment money, so I personally like to preserve my cash. So, chocolate or vanilla?