How to fund our 3rd property?

[Adam Christopher Zaleski]

My wife and I currently have two rentals and we are looking to purchase our 3rd property as a primary residence in August 2017. The basic question is, "Do we put 5% down, or do we re-finance a rental property so we can put 20% down."

Rental #1: Single family home in Colorado (4 bed/2 bath). Purchased in 2007 for 182K, plus10K of rehab costs. Mortgage, taxes and insurance is $950. Current rent is $2,000/month, but rent will be going up to $2,200/month in August 2017. House is worth around 320K. I have 115K left on the mortgage at 4.75%. Because I refinanced in 2009, we are currently in our 7th year of the mortgage. A total of $301 is going to principle and $458 is going toward interest.

Rental #2: Single family home in Florida (3 bed/2 bath). Purchased in 2012 for 95K, plus 16K of rehab costs. Mortgage, taxes, insurance and PMI is $665/month. Current rent is $1700/month, but rent will be going up to $1750/month in August 2017. House is worth around 225K and I have 78K left on the mortgage at 4%. A total of $170 is going to principle, $260 toward interest and $42 toward PMI. Once the loan gets below 74K, the PMI will go away.

Potential Home Purchase: 3 bed/2 bath with an additional 1 bed/1 bath ADU for around 500K. Potential rent on the ADU is $1,100-$1,300. Something around 500K would require less than 10K in rehab costs and pretty much be cosmetic. It's possible to get something around 425K-450K, but the rehab costs would be closer to 25K-50K and a larger project.

We currently have 25,000 in cash. We can save around $2,000/month. We should have around 45,000 in cash in August 2017.

If we put 5% down on a primary residence we will have to pay $314/month in PMI. We could put 20% down, if we refinanced rental house #1.

To me, it seems like a complicated math question.  Any ideas on the pros and cons?