Which refinance strategy should I choose ?

[Karoly Holczhauser]

Purchased property in 2018 Q2, $50k downpayment; $200k loan; price was $249k

Right now I have 30 years fixed, 4.375% ARP ; $1533 / month as payment (p&i + tax incl) ; 225 HOA / m

Option 1: 30 years, 2.8% ARP; $1340 / month (p&i + tax incl) as estimated payment 

Option 2: 30 years, $30k down, 2.8% ARP; $1240 / month (p&i + tax incl) as estimated payment

Option 3: 15 years ; 2.5% ; $1840 / month (p&i + tax incl) as estimated payment

Option 4: 15 years ; $30k down ; $1600 / month (p&i + tax incl) estimated payment

Unit is being rented as of now for $1650 / m until 2021 July.

I am not sure I can rent it out for more than $1700 / month. I would like to have unit to pay for herself over the years, without the need to put $100-$200 there in every month to match mortgage amount. 

I am in favor to put $30k down for 15 years, so I can have this as a savings for college to my son. Is it a bad idea to increase equity with refinancing? I never heard that people do it, it's usually the other way around. 

Any advice is highly appreciated.