How to Scale Investment Property

[Steven Peck]

I need advice about scaling and see 3 options ahead. My wife and I have rented out a 3/2 single family in Jax, FL since 2009.  
#1 Sell: The house has ~110k in equity.  Does it make sense to sell in order to buy a multifamily?
#2 Refi: I'll only see about 45-50K in a refi and have smaller net operating income moving forward. Rates will be higher too. 
#3 Stay the Course: It rents for $1625 and it cashflows ~500 per/month after 10% management fees.  Rate is 4.375%

How can I buy another property without jeopardizing our current position? 

How can I find a seller financing deal that requires less that 20% down?