What to do after first rental purchase?

[Brittany Fife]

I just purchased my first duplex a few months ago. I also have a single family I am renting out. The single family has an equity line on it. The duplex is FHA owner occupied. I was wondering how to get a four-plex. Should I pay off the mortgage and equity line as fast as I can and then refinance the mortgage, or should I pool up a large amount of money for a down-payment. If I save up my money I could purchase a four-plex with 20% down and then I would not have to refinance the duplex mortgage. I don't know which is better and which would give me a loan faster. Do you guys have any advice for me? I want to make sure I don't waste my time/money and that I get into more investments as soon as possible. The duplex and single family are my FIRST rental income so I believe I would need at least one year steady income for the financier to see that I am able to make income this way (track record).