Trying to determine best approach for getting 2nd mortgage

[Brick Biermann]

Hello All,

So I purchased a 4 family home several years ago for $455K with my girlfriend with an FHA loan, only putting 3.5% down and have rehabbed it to the point where 3 units are rented out while we live in the 4th unit. The rental income from the 3 units alone completely covers the cost of the mortgage so if we were to rent out the unit we reside in, I estimate we'd have a surplus of $1400 a month accounting for an avg. of $500 put aside for monthly maintenance expenses.

I haven't appraised my home since the purchase but based on recent comps, and the # of years I've had the existing mortgage I'd estimate to have approx. 50K in equity.

My girlfriend and I would now like to purchase a single family home. We both have descent credit scores (above 750 Fico), nominal amount of debt, have a combined income of $125K (I earn 80K, she earns 45K) and would like to get some feedback to determine the best approach when applying for a second mortgage. Ideally I'd like to have 20% down for the 2nd home but would also like to know if there are other options available with putting less down. Any advice is appreciated.